Pub Date : 2015-08-07DOI: 10.1002/0471264180.OR087.02
Nanyan Fu, T. Tidwell
Vinylketenes may be prepared by the typical procedures used for other ketenes, and are usually highly reactive, except when bulky groups and silyl substituents are present. They are extensively utilized in cycloaddition reactions and electrocyclizations, including dimerizations, inter- and intramolecular reactions with alkenes, alkynes, imines, and carbonyl groups, and intramolecular reactions with aryl and heteroaryl groups. These pericyclic reactions are widely used in syntheses of carbocyclic and heterocyclic products, and are particularly useful for the preparation of β-lactams and β-lactones. Allenylketenes and alkynylketenes also undergo cycloaddition and electrocyclic reactions. Keywords: Vinylketenes; allenylketenes; alkynylketenes; cycloaddition; electrocyclization; diazo ketones; cyclobutenones; cyclohexadienones; acyl chlorides; β-lactams; β-lactones
{"title":"Cycloaddition and Electrocyclic Reactions of Vinylketenes, Allenylketenes, and Alkynylketenes","authors":"Nanyan Fu, T. Tidwell","doi":"10.1002/0471264180.OR087.02","DOIUrl":"https://doi.org/10.1002/0471264180.OR087.02","url":null,"abstract":"Vinylketenes may be prepared by the typical procedures used for other ketenes, and are usually highly reactive, except when bulky groups and silyl substituents are present. They are extensively utilized in cycloaddition reactions and electrocyclizations, including dimerizations, inter- and intramolecular reactions with alkenes, alkynes, imines, and carbonyl groups, and intramolecular reactions with aryl and heteroaryl groups. These pericyclic reactions are widely used in syntheses of carbocyclic and heterocyclic products, and are particularly useful for the preparation of β-lactams and β-lactones. Allenylketenes and alkynylketenes also undergo cycloaddition and electrocyclic reactions. \u0000 \u0000 \u0000Keywords: \u0000 \u0000Vinylketenes; \u0000allenylketenes; \u0000alkynylketenes; \u0000cycloaddition; \u0000electrocyclization; \u0000diazo ketones; \u0000cyclobutenones; \u0000cyclohexadienones; \u0000acyl chlorides; \u0000β-lactams; \u0000β-lactones","PeriodicalId":19539,"journal":{"name":"Organic Reactions","volume":"40 1","pages":"257-506"},"PeriodicalIF":0.0,"publicationDate":"2015-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90949350","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-01-27DOI: 10.1002/0471264180.OR086.01
J. W. Kramer, J. M. Rowley, G. Coates
This review summarizes the field of metal-catalyzed ring-expanding carbonylation of epoxides. Specifically, epoxide carbonylation to -, -, and -lactones is reviewed, in addition to epoxide carbonylation to succinic anhydrides, 1,3-oxazinane-2,4-diones and 1,3-oxathiolan-2-ones. For each reaction, the mechanism of catalysis and control of stereochemistry are discussed and the scope and limitations of the catalysts are considered. Experimental conditions and procedures are also presented. In addition, non-carbonylative routes preparing similar products are compared. Keywords: Carbonylation; carbon-carbon bond formation; carbon monoxide; catalysis; epoxide; lactone; ring-expansion; succinic anhydride
{"title":"Ring‐Expanding Carbonylation of Epoxides","authors":"J. W. Kramer, J. M. Rowley, G. Coates","doi":"10.1002/0471264180.OR086.01","DOIUrl":"https://doi.org/10.1002/0471264180.OR086.01","url":null,"abstract":"This review summarizes the field of metal-catalyzed ring-expanding carbonylation of epoxides. Specifically, epoxide carbonylation to -, -, and -lactones is reviewed, in addition to epoxide carbonylation to succinic anhydrides, 1,3-oxazinane-2,4-diones and 1,3-oxathiolan-2-ones. For each reaction, the mechanism of catalysis and control of stereochemistry are discussed and the scope and limitations of the catalysts are considered. Experimental conditions and procedures are also presented. In addition, non-carbonylative routes preparing similar products are compared. \u0000 \u0000 \u0000Keywords: \u0000 \u0000Carbonylation; \u0000carbon-carbon bond formation; \u0000carbon monoxide; \u0000catalysis; \u0000epoxide; \u0000lactone; \u0000ring-expansion; \u0000succinic anhydride","PeriodicalId":19539,"journal":{"name":"Organic Reactions","volume":"16 1","pages":"1-104"},"PeriodicalIF":0.0,"publicationDate":"2015-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73718415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-01-27DOI: 10.1002/0471264180.OR086.02
A. Koskinen, A. Kataja
Aldehydes may be dimerized to symmetric esters via the Tishchenko reaction. This process is traditionally catalyzed by aluminum alkoxides, but a wide variety of different metal catalysts has been explored and implemented, ranging from simple alkali metal compounds to actinoid complexes. The mechanistic key step is a hydride transfer from a hemiacetal intermediate to an aldehyde, both participants being coordinated to the metal catalyst in the transition state. Recent research on the Tishchenko reaction has especially focused on the controlled synthesis of unsymmetrical esters. In the aldol-Tishchenko variant, an aldol reaction takes place first between two aldehydes, or a ketone and an aldehyde. In the subsequent Tishchenko step, another aldehyde molecule coordinates to the aldol product, forming a hemiacetal intermediate. An intramolecular hydrogen transfer from the hemiacetal to the carbonyl group takes place, giving a 1,3-diol monoester product. With -hydroxy ketone substrates, the reaction is highly diastereoselective towards 1,3-anti-diols due to a highly organized six-membered transition state promoted by coordination of a metal catalyst to both the hemiacetal and carbonyl groups. Thus, recent research has strongly focused on the development of direct catalytic asymmetric aldol-Tishchenko reactions. The Evans-Tishchenko reaction is a further variant of the aldol-Tishchenko reaction, being used to reduce preformed -hydroxy ketones to anti-1,3-diols under relatively mild conditions. This method is applied to various total syntheses of natural products. Samarium iodide is commonly used as the catalyst, and nearly any aldehyde is suitable as the reducing agent. The reaction has also been exploited in a reverse fashion to oxidize complex aldehydes to carboxylic acids using a simple sacrificial -hydroxy ketone as the oxidant. This review covers the literature from the discovery of the Tishchenko reaction in 1887 up to early 2014. Different catalyst systems for both Tishchenko and aldol-Tishchenko reactions are discussed and compared in the “Scope and Limitations” section, and the state of the art in substrate complexity for the reaction is presented in the “Tabular Survey”.
{"title":"The Tishchenko Reaction","authors":"A. Koskinen, A. Kataja","doi":"10.1002/0471264180.OR086.02","DOIUrl":"https://doi.org/10.1002/0471264180.OR086.02","url":null,"abstract":"Aldehydes may be dimerized to symmetric esters via the Tishchenko reaction. This process is traditionally catalyzed by aluminum alkoxides, but a wide variety of different metal catalysts has been explored and implemented, ranging from simple alkali metal compounds to actinoid complexes. The mechanistic key step is a hydride transfer from a hemiacetal intermediate to an aldehyde, both participants being coordinated to the metal catalyst in the transition state. Recent research on the Tishchenko reaction has especially focused on the controlled synthesis of unsymmetrical esters. \u0000 \u0000 \u0000 \u0000In the aldol-Tishchenko variant, an aldol reaction takes place first between two aldehydes, or a ketone and an aldehyde. In the subsequent Tishchenko step, another aldehyde molecule coordinates to the aldol product, forming a hemiacetal intermediate. An intramolecular hydrogen transfer from the hemiacetal to the carbonyl group takes place, giving a 1,3-diol monoester product. With -hydroxy ketone substrates, the reaction is highly diastereoselective towards 1,3-anti-diols due to a highly organized six-membered transition state promoted by coordination of a metal catalyst to both the hemiacetal and carbonyl groups. Thus, recent research has strongly focused on the development of direct catalytic asymmetric aldol-Tishchenko reactions. \u0000 \u0000 \u0000 \u0000The Evans-Tishchenko reaction is a further variant of the aldol-Tishchenko reaction, being used to reduce preformed -hydroxy ketones to anti-1,3-diols under relatively mild conditions. This method is applied to various total syntheses of natural products. Samarium iodide is commonly used as the catalyst, and nearly any aldehyde is suitable as the reducing agent. The reaction has also been exploited in a reverse fashion to oxidize complex aldehydes to carboxylic acids using a simple sacrificial -hydroxy ketone as the oxidant. \u0000 \u0000 \u0000 \u0000This review covers the literature from the discovery of the Tishchenko reaction in 1887 up to early 2014. Different catalyst systems for both Tishchenko and aldol-Tishchenko reactions are discussed and compared in the “Scope and Limitations” section, and the state of the art in substrate complexity for the reaction is presented in the “Tabular Survey”.","PeriodicalId":19539,"journal":{"name":"Organic Reactions","volume":"117 1","pages":"105-410"},"PeriodicalIF":0.0,"publicationDate":"2015-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75467058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-04-22DOI: 10.1002/0471264180.OR084.02
Brian W Michel, Laura D. Steffens, M. Sigman
Terminal alkene substrates can be converted to methyl ketone products via a palladium-catalyzed process known as the Wacker oxidation. This process has found widespread application in targeted synthesis, since alkene substrates are easily accessed and unreactive under diverse reaction conditions substrates and the resultant carbonyl products are common precursors for diverse synthetic manipulations. This chapter covers the application of the Wacker oxidation and variations of the Wacker oxidation to various types of alkene substrates. The literature covered spans the inception of the reaction in 1959 through November 2012. A discussion of the current mechanistic understanding is presented, emphasizing considerations that are relevant to synthetic application, including how the nature of the alkene substrate and nucleophiles other than water are proposed to influence the mechanistic pathways and ultimately the product distribution. The “Scope and Limitations” section is separated into discussions relating to functional group tolerance, the influence of heteroatoms proximal to the alkene substrate, and Wacker-type oxidations that do not result in carbonyl products, such as cyclization reactions and aza-Wacker reactions. Select applications of the Wacker oxidation in total synthesis are presented, as well as a comparison to other methods and examples of experimental conditions. Keywords: Wacker oxidation(s); palladium-catalyzed; nucleopalladation; oxypalladation; alkene(s); olefin(s); ketone(s); Markovnikov addition; anti-Markovnikov addition; ligand-modulation; molecular oxygen; tert-butylhydroperoxide; Benzoquinone; allylic alcohol(s); homoallylic alchol(s); allylic amine(s); homoallylic amine(s); Wacker cyclization; acetal(s); aza-Wacker
{"title":"Wacker Oxidation, The","authors":"Brian W Michel, Laura D. Steffens, M. Sigman","doi":"10.1002/0471264180.OR084.02","DOIUrl":"https://doi.org/10.1002/0471264180.OR084.02","url":null,"abstract":"Terminal alkene substrates can be converted to methyl ketone products via a palladium-catalyzed process known as the Wacker oxidation. This process has found widespread application in targeted synthesis, since alkene substrates are easily accessed and unreactive under diverse reaction conditions substrates and the resultant carbonyl products are common precursors for diverse synthetic manipulations. \u0000 \u0000 \u0000 \u0000This chapter covers the application of the Wacker oxidation and variations of the Wacker oxidation to various types of alkene substrates. The literature covered spans the inception of the reaction in 1959 through November 2012. \u0000 \u0000 \u0000 \u0000A discussion of the current mechanistic understanding is presented, emphasizing considerations that are relevant to synthetic application, including how the nature of the alkene substrate and nucleophiles other than water are proposed to influence the mechanistic pathways and ultimately the product distribution. The “Scope and Limitations” section is separated into discussions relating to functional group tolerance, the influence of heteroatoms proximal to the alkene substrate, and Wacker-type oxidations that do not result in carbonyl products, such as cyclization reactions and aza-Wacker reactions. Select applications of the Wacker oxidation in total synthesis are presented, as well as a comparison to other methods and examples of experimental conditions. \u0000 \u0000 \u0000Keywords: \u0000 \u0000Wacker oxidation(s); \u0000palladium-catalyzed; \u0000nucleopalladation; \u0000oxypalladation; \u0000alkene(s); \u0000olefin(s); \u0000ketone(s); \u0000Markovnikov addition; \u0000anti-Markovnikov addition; \u0000ligand-modulation; \u0000molecular oxygen; \u0000tert-butylhydroperoxide; \u0000Benzoquinone; \u0000allylic alcohol(s); \u0000homoallylic alchol(s); \u0000allylic amine(s); \u0000homoallylic amine(s); \u0000Wacker cyclization; \u0000acetal(s); \u0000aza-Wacker","PeriodicalId":19539,"journal":{"name":"Organic Reactions","volume":"62 1","pages":"75-414"},"PeriodicalIF":0.0,"publicationDate":"2014-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88931861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-11-22DOI: 10.1002/0471264180.OR082.01
T. Takeda*, A. Tsubouchi
The McMurry coupling reaction has been recognized as one of the most efficient methods for the synthesis of alkenes from carbonyl compounds. This reaction can be applied to the preparation of various alkenes that are otherwise difficult to prepare. For example, sterically congested tetrasubstituted alkenes as well as medium to large membered rings involving natural products may be accessed via this process. This coupling utilizes various low-valent titanium reagents generated by the reduction of titanium (III or IV) chloride with K, Zn, LiAlH4, C8K, amongst others. Furthermore, a variety of low-valent metal species other than titanium, including aluminum, zirconium, niobium, molybdenum, indium, tungsten, and samarium, have also been found to promote the reductive coupling of carbonyl compounds. The scope and limitations of these reagent systems are reviewed in this chapter, together with the stereochemistry and reaction mechanism. This reaction is categorized into four coupling modes: i) homocoupling giving symmetrical alkenes, ii) mixed coupling giving unsymmetrical alkenes, iii) intramolecular coupling giving cycloalkenes, and iv) tandem coupling giving cyclic polyenes. Characteristics of these reaction modes are described briefly. A selection of synthetic applications are reviewed, including examples of the preparation of sterically congested and strained alkenes, medium to large-ring compounds, biologically active targets, as well as substrates applicable in material science. Experimental conditions used for this versatile process are summarized to assist the choice of suitable conditions. Keywords: McMurry coupling; low-valent titanium; titanium-carbene complexes; carbonyl compounds; homocoupling; mixed coupling; intramolecular coupling; tandem coupling; natural products; sterically congested alkene; strained alkenes; cyclophanes; helicenes; medium ring compounds
{"title":"The McMurry Coupling and Related Reactions","authors":"T. Takeda*, A. Tsubouchi","doi":"10.1002/0471264180.OR082.01","DOIUrl":"https://doi.org/10.1002/0471264180.OR082.01","url":null,"abstract":"The McMurry coupling reaction has been recognized as one of the most efficient methods for the synthesis of alkenes from carbonyl compounds. This reaction can be applied to the preparation of various alkenes that are otherwise difficult to prepare. For example, sterically congested tetrasubstituted alkenes as well as medium to large membered rings involving natural products may be accessed via this process. This coupling utilizes various low-valent titanium reagents generated by the reduction of titanium (III or IV) chloride with K, Zn, LiAlH4, C8K, amongst others. Furthermore, a variety of low-valent metal species other than titanium, including aluminum, zirconium, niobium, molybdenum, indium, tungsten, and samarium, have also been found to promote the reductive coupling of carbonyl compounds. The scope and limitations of these reagent systems are reviewed in this chapter, together with the stereochemistry and reaction mechanism. This reaction is categorized into four coupling modes: i) homocoupling giving symmetrical alkenes, ii) mixed coupling giving unsymmetrical alkenes, iii) intramolecular coupling giving cycloalkenes, and iv) tandem coupling giving cyclic polyenes. Characteristics of these reaction modes are described briefly. A selection of synthetic applications are reviewed, including examples of the preparation of sterically congested and strained alkenes, medium to large-ring compounds, biologically active targets, as well as substrates applicable in material science. Experimental conditions used for this versatile process are summarized to assist the choice of suitable conditions. \u0000 \u0000 \u0000Keywords: \u0000 \u0000McMurry coupling; \u0000low-valent titanium; \u0000titanium-carbene complexes; \u0000carbonyl compounds; \u0000homocoupling; \u0000mixed coupling; \u0000intramolecular coupling; \u0000tandem coupling; \u0000natural products; \u0000sterically congested alkene; \u0000strained alkenes; \u0000cyclophanes; \u0000helicenes; \u0000medium ring compounds","PeriodicalId":19539,"journal":{"name":"Organic Reactions","volume":"61 5 1","pages":"1-470"},"PeriodicalIF":0.0,"publicationDate":"2013-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86800598","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-11-22DOI: 10.1002/0471264180.OR082.02
S. G. Nelson, R. Dura, T. Peelen
Ketenes are among the few synthetic building blocks that undergo facile thermal [2 + 2] and [4 + 2] cycloadditions, yielding cyclobutanes, β-lactones, β-lactams, dioxins, quinoxalines, thiazinones, pyranones, and other useful carbo- and heterocycles. In addition to substrate structure, the presence of Lewis acids and bases can have a decisive effect on product outcome by diverting ketene reactivity to different cycloaddition manifolds. This comprehensive review focuses on catalyzed enantioselective ketene [2 + 2] and [4 + 2] cycloadditions in which the asymmetric induction is derived solely from the catalyst complex. Accordingly, diastereoselective cycloadditions are described only when they are relevant to a catalytic asymmetric reaction variant. Molecular orbital interactions are correlated to the electronic structure of ketenes and used to explain ketene reaction pathways. Cinchona alkaloids play an important role in Lewis base catalyzed asymmetric carbonyl and imine cycloadditions, whereas Al(III)-, Fe(II)-, Ti(IV)-, and Cu(II)-complexes are mainly responsible for Lewis acid catalyzed asymmetric transformations. Carbene catalysts are also significant for both ketene–carbonyl and ketene–imine cycloadditions. The subject cycloaddition protocol is also compared with other methods, including Mannich- and aldol-based approaches to β-lactams and β-lactones, nitrone–alkyne and hetero Diels–Alder reactions, and the catalytic asymmetric allylation–lactonization. Keywords: cycloadditions; ketenes; β-lactams; β-lactones
{"title":"Catalytic Asymmetric Ketene [2 + 2] and [4 + 2] Cycloadditions","authors":"S. G. Nelson, R. Dura, T. Peelen","doi":"10.1002/0471264180.OR082.02","DOIUrl":"https://doi.org/10.1002/0471264180.OR082.02","url":null,"abstract":"Ketenes are among the few synthetic building blocks that undergo facile thermal [2 + 2] and [4 + 2] cycloadditions, yielding cyclobutanes, β-lactones, β-lactams, dioxins, quinoxalines, thiazinones, pyranones, and other useful carbo- and heterocycles. In addition to substrate structure, the presence of Lewis acids and bases can have a decisive effect on product outcome by diverting ketene reactivity to different cycloaddition manifolds. \u0000 \u0000 \u0000 \u0000This comprehensive review focuses on catalyzed enantioselective ketene [2 + 2] and [4 + 2] cycloadditions in which the asymmetric induction is derived solely from the catalyst complex. Accordingly, diastereoselective cycloadditions are described only when they are relevant to a catalytic asymmetric reaction variant. Molecular orbital interactions are correlated to the electronic structure of ketenes and used to explain ketene reaction pathways. \u0000 \u0000 \u0000 \u0000Cinchona alkaloids play an important role in Lewis base catalyzed asymmetric carbonyl and imine cycloadditions, whereas Al(III)-, Fe(II)-, Ti(IV)-, and Cu(II)-complexes are mainly responsible for Lewis acid catalyzed asymmetric transformations. Carbene catalysts are also significant for both ketene–carbonyl and ketene–imine cycloadditions. \u0000 \u0000 \u0000 \u0000The subject cycloaddition protocol is also compared with other methods, including Mannich- and aldol-based approaches to β-lactams and β-lactones, nitrone–alkyne and hetero Diels–Alder reactions, and the catalytic asymmetric allylation–lactonization. \u0000 \u0000 \u0000Keywords: \u0000 \u0000cycloadditions; \u0000ketenes; \u0000β-lactams; \u0000β-lactones","PeriodicalId":19539,"journal":{"name":"Organic Reactions","volume":"53 1","pages":"471-621"},"PeriodicalIF":0.0,"publicationDate":"2013-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79304099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-09-20DOI: 10.1002/0471264180.OR081.01
A. Krapcho, E. Ciganek
The Krapcho reaction involves esters with α-electron-withdrawing substituents such as malonates, β-keto esters, and α-cyano esters, which undergo dealkoxycarbonylation on being heated in polar aprotic solvents (such as DMSO, DMF, or HMPT) in the presence of water, or in polar aprotic solvents with water in the presence of added salts (such as NaCN, NaCl, LiCl, LiI, or MgCl2). This procedure avoids the use of strongly aqueous acidic and alkaline conditions and tolerates many functional and protecting groups. The chapter presents the mechanistic aspects of this procedure, which include reaction parameters such as solvents, salts, other additives, and the use of microwave irradiation. The diastereoselectivity of protonation of the enolate intermediate leading to the dealkoxycarbonylated products is discussed. Trapping of the intermediate enolate by electrophiles other than a proton is illustrated. Potential side reactions and same-pot subsequent reactions of substrates are discussed along with functional-group compatibility for halogens and nitrogen, oxygen, sulfur, selenium, and carbon functional groups. Several examples of applications of this methodology for the synthesis of natural products along with experimental conditions and procedures are presented. Closely related methods are discussed in the Comparison with Other Methods section. The tables, which consist of 371 pages, are grouped according to substrate structure. Selective entries for other methods (excluding classical aqueous acidic or basic methods) are included in the tabular survey for comparative purposes. Keywords: dealkoxycarbonylation; esters with α-electron-withdrawing groups
{"title":"The Krapcho Dealkoxycarbonylation Reaction of Esters with α‐Electron‐Withdrawing Substituents","authors":"A. Krapcho, E. Ciganek","doi":"10.1002/0471264180.OR081.01","DOIUrl":"https://doi.org/10.1002/0471264180.OR081.01","url":null,"abstract":"The Krapcho reaction involves esters with α-electron-withdrawing substituents such as malonates, β-keto esters, and α-cyano esters, which undergo dealkoxycarbonylation on being heated in polar aprotic solvents (such as DMSO, DMF, or HMPT) in the presence of water, or in polar aprotic solvents with water in the presence of added salts (such as NaCN, NaCl, LiCl, LiI, or MgCl2). This procedure avoids the use of strongly aqueous acidic and alkaline conditions and tolerates many functional and protecting groups. The chapter presents the mechanistic aspects of this procedure, which include reaction parameters such as solvents, salts, other additives, and the use of microwave irradiation. The diastereoselectivity of protonation of the enolate intermediate leading to the dealkoxycarbonylated products is discussed. Trapping of the intermediate enolate by electrophiles other than a proton is illustrated. Potential side reactions and same-pot subsequent reactions of substrates are discussed along with functional-group compatibility for halogens and nitrogen, oxygen, sulfur, selenium, and carbon functional groups. \u0000 \u0000 \u0000 \u0000Several examples of applications of this methodology for the synthesis of natural products along with experimental conditions and procedures are presented. Closely related methods are discussed in the Comparison with Other Methods section. The tables, which consist of 371 pages, are grouped according to substrate structure. Selective entries for other methods (excluding classical aqueous acidic or basic methods) are included in the tabular survey for comparative purposes. \u0000 \u0000 \u0000Keywords: \u0000 \u0000dealkoxycarbonylation; \u0000esters with α-electron-withdrawing groups","PeriodicalId":19539,"journal":{"name":"Organic Reactions","volume":"C-19 1","pages":"1-536"},"PeriodicalIF":0.0,"publicationDate":"2013-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85059177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-04-19DOI: 10.1002/0471264180.OR083.02
S. Pyne, M. Tang
The boronic acid Mannich reaction is a three-component reaction between a carbonyl compound (aldehyde or ketone), an amine (primary or secondary) and a boronic acid. This chapter addresses the mechanism, stereochemistry, and the scope and limitations of each of the three components of this reaction. Some typical experimental conditions are provided along with a comprehensive Tabular Survey. This three-component reaction is extremely versatile for preparing important chiral starting materials for the synthesis of molecules of biological interest, including chiral α-amino acids, 1,2-amino alcohols, 2-aminoalkyl phenols, heterocycles, and alkaloids as shown in the general scheme below. Keywords: multicomponent reactions; Petasis reaction
{"title":"The Boronic Acid Mannich Reaction","authors":"S. Pyne, M. Tang","doi":"10.1002/0471264180.OR083.02","DOIUrl":"https://doi.org/10.1002/0471264180.OR083.02","url":null,"abstract":"The boronic acid Mannich reaction is a three-component reaction between a carbonyl compound (aldehyde or ketone), an amine (primary or secondary) and a boronic acid. This chapter addresses the mechanism, stereochemistry, and the scope and limitations of each of the three components of this reaction. Some typical experimental conditions are provided along with a comprehensive Tabular Survey. \u0000 \u0000 \u0000 \u0000This three-component reaction is extremely versatile for preparing important chiral starting materials for the synthesis of molecules of biological interest, including chiral α-amino acids, 1,2-amino alcohols, 2-aminoalkyl phenols, heterocycles, and alkaloids as shown in the general scheme below. \u0000 \u0000 \u0000Keywords: \u0000 \u0000multicomponent reactions; \u0000Petasis reaction","PeriodicalId":19539,"journal":{"name":"Organic Reactions","volume":"17 1","pages":"211-498"},"PeriodicalIF":0.0,"publicationDate":"2013-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87360170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-04-19DOI: 10.1002/0471264180.OR079.02
N. Simpkins, M. D. Weller
Lithium dialkylamides, especially lithium diisopropylamide (LDA), are valuable bases in organic synthesis but it is only since 1980 that their chiral counterparts have found application in reactions that can be broadly defined as asymmetric deprotonations. This chapter provides a comprehensive overview of all selective deprotonation processes mediated by chiral lithium amides, including desymmetrizations, kinetic resolutions, and other applications such as regioselective enolizations of chiral substrates. The chapter covers the entire substrate scope of chiral lithium amide deprotonation reactions, which includes rearrangement of epoxides to allylic alcohols, enolizations of carbonyl compounds (principally, but not exclusively, cyclic ketones), and metalations of organometallics (especially tricarbonyl(η6-arene)chromium(0) complexes) and miscellaneous phosphorous- or sulfur-containing compounds. It is possible to perform some benchmark reactions under “catalytic conditions,” i.e., using substoichiometic quantities of chiral lithium amide, particularly epoxide rearrangements. The capability of deprotonations, mediated by chiral lithium amides, to deliver non-racemic intermediates with acceptable selectivity for target synthesis is amply illustrated by the examples included in the review. In particular, the desymmetrization of conformationally biased prochiral cyclic ketones has become a well-established strategy for organic synthesis, and has seen significant application in target-oriented synthesis. Keywords: enantioselectivity; stereochemistry; asymmetric deprotonation; lithiation; rearrangements; lithium amides; epoxides; cyclic ketones; enolates; cyclic imides; bridgehead substitution; tricarbonyl(η6-arene)chromium(0) complexes; kinetic resolution; catalysis; polymeric reagents
{"title":"Asymmetric Transformations by Deprotonation Using Chiral Lithium Amides","authors":"N. Simpkins, M. D. Weller","doi":"10.1002/0471264180.OR079.02","DOIUrl":"https://doi.org/10.1002/0471264180.OR079.02","url":null,"abstract":"Lithium dialkylamides, especially lithium diisopropylamide (LDA), are valuable bases in organic synthesis but it is only since 1980 that their chiral counterparts have found application in reactions that can be broadly defined as asymmetric deprotonations. This chapter provides a comprehensive overview of all selective deprotonation processes mediated by chiral lithium amides, including desymmetrizations, kinetic resolutions, and other applications such as regioselective enolizations of chiral substrates. \u0000 \u0000 \u0000 \u0000The chapter covers the entire substrate scope of chiral lithium amide deprotonation reactions, which includes rearrangement of epoxides to allylic alcohols, enolizations of carbonyl compounds (principally, but not exclusively, cyclic ketones), and metalations of organometallics (especially tricarbonyl(η6-arene)chromium(0) complexes) and miscellaneous phosphorous- or sulfur-containing compounds. \u0000 \u0000 \u0000 \u0000It is possible to perform some benchmark reactions under “catalytic conditions,” i.e., using substoichiometic quantities of chiral lithium amide, particularly epoxide rearrangements. The capability of deprotonations, mediated by chiral lithium amides, to deliver non-racemic intermediates with acceptable selectivity for target synthesis is amply illustrated by the examples included in the review. In particular, the desymmetrization of conformationally biased prochiral cyclic ketones has become a well-established strategy for organic synthesis, and has seen significant application in target-oriented synthesis. \u0000 \u0000 \u0000Keywords: \u0000 \u0000enantioselectivity; \u0000stereochemistry; \u0000asymmetric deprotonation; \u0000lithiation; \u0000rearrangements; \u0000lithium amides; \u0000epoxides; \u0000cyclic ketones; \u0000enolates; \u0000cyclic imides; \u0000bridgehead substitution; \u0000tricarbonyl(η6-arene)chromium(0) complexes; \u0000kinetic resolution; \u0000catalysis; \u0000polymeric reagents","PeriodicalId":19539,"journal":{"name":"Organic Reactions","volume":"97 1","pages":"317-636"},"PeriodicalIF":0.0,"publicationDate":"2013-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82750762","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-04-19DOI: 10.1002/0471264180.OR080.02
D. Hodgson, A. Labande, S. Muthusamy
[3 + 2] cycloadditions of carbonyl ylides with dipolarophiles provides a synthetically powerful way to make a variety of 5-membered oxacycles. One of the best ways to generate carbonyl ylide intermediates is by transition metal-catalyzed loss of nitrogen from diazocarbonyl compounds and trapping of the resultant metallocarbenes by a carbonyl group. This chapter covers the metal-catalyzed intra- and intermolecular cycloadditions of carbonyl ylides derived from diazocarbonyl compounds with various dipolarophiles. The literature up to the end of 2011 is covered. A comprehensive discussion is provided of mechanism and stereochemistry, regioselectivity, stereoselectivity, and asymmetric cycloadditions. The structural scope at the diazo group, of the carbonyl group forming the ylide, and of the dipolarophile is delineated. A systematic analysis is presented of the scope and limitations of intra- and intermolecular cycloadditions of cyclic diazocarbonyl-derived carbonyl ylides from ketones, esters, amides or imides, including cycloadditions of aromatic pyrylium and isomunchnone ylides. The generation of acyclic carbonyl ylides from aldehydes, ketones, or imides and their cycloadditions is also reviewed. Finally, important applications to the total synthesis of natural products and a critical comparison with other methods for carbonyl ylide generation-cycloaddition are presented. Keywords: cycloaddition reaction(s); [3 + 2] reaction(S); intermolecular cycloaddition(s); intramolecular cycloaddition(s); metal catalyzed; diazo compound(s); carbonyl ylide(s); pyrylium(s); isomunchnone(s); natural product(s); asymmetric catalysis; stereochemistry; method comparisons; experimental procedures
{"title":"Cycloadditions of Carbonyl Ylides Derived from Diazocarbonyl Compounds","authors":"D. Hodgson, A. Labande, S. Muthusamy","doi":"10.1002/0471264180.OR080.02","DOIUrl":"https://doi.org/10.1002/0471264180.OR080.02","url":null,"abstract":"[3 + 2] cycloadditions of carbonyl ylides with dipolarophiles provides a synthetically powerful way to make a variety of 5-membered oxacycles. One of the best ways to generate carbonyl ylide intermediates is by transition metal-catalyzed loss of nitrogen from diazocarbonyl compounds and trapping of the resultant metallocarbenes by a carbonyl group. \u0000 \u0000 \u0000 \u0000This chapter covers the metal-catalyzed intra- and intermolecular cycloadditions of carbonyl ylides derived from diazocarbonyl compounds with various dipolarophiles. The literature up to the end of 2011 is covered. \u0000 \u0000 \u0000 \u0000A comprehensive discussion is provided of mechanism and stereochemistry, regioselectivity, stereoselectivity, and asymmetric cycloadditions. The structural scope at the diazo group, of the carbonyl group forming the ylide, and of the dipolarophile is delineated. A systematic analysis is presented of the scope and limitations of intra- and intermolecular cycloadditions of cyclic diazocarbonyl-derived carbonyl ylides from ketones, esters, amides or imides, including cycloadditions of aromatic pyrylium and isomunchnone ylides. The generation of acyclic carbonyl ylides from aldehydes, ketones, or imides and their cycloadditions is also reviewed. Finally, important applications to the total synthesis of natural products and a critical comparison with other methods for carbonyl ylide generation-cycloaddition are presented. \u0000 \u0000 \u0000Keywords: \u0000 \u0000cycloaddition reaction(s); \u0000[3 + 2] reaction(S); \u0000intermolecular cycloaddition(s); \u0000intramolecular cycloaddition(s); \u0000metal catalyzed; \u0000diazo compound(s); \u0000carbonyl ylide(s); \u0000pyrylium(s); \u0000isomunchnone(s); \u0000natural product(s); \u0000asymmetric catalysis; \u0000stereochemistry; \u0000method comparisons; \u0000experimental procedures","PeriodicalId":19539,"journal":{"name":"Organic Reactions","volume":"39 1","pages":"133-496"},"PeriodicalIF":0.0,"publicationDate":"2013-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77435174","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：