Kinetics of the hydrolysis of diaryldiacyloxyspirosulfuranes leading to sulfoxides have been studied under pseudo-first-order conditions in dioxane–water mixtures. It has been found that high solvent polarities and ionic strengths increase the reaction rate. The reaction is also promoted by electron-donating substituents (ρ–0.52). Strong acids have a catalytic effect on the reaction in which case the substituent effect is more pronounced (ρ–1.55). In neutral medium the deuterium solvent isotope effect is kH2O/kD2O 1.66, while in acidic medium the ratio of catalytic constants is found to be 0.56. The rate of the reaction is greatly increased with the increasing size of the spiroring (from 5 to 7) in the sulfurane. Kinetic data suggest a dissociative reaction mechanism.
{"title":"Diaryldiacyloxyspirosulfuranes. Part 4. A kinetic study on the mechanism of hydrolysis","authors":"E. Vass, F. Ruff, I. Kapovits, J. Rábai, D. Szabó","doi":"10.1039/P29930000855","DOIUrl":"https://doi.org/10.1039/P29930000855","url":null,"abstract":"Kinetics of the hydrolysis of diaryldiacyloxyspirosulfuranes leading to sulfoxides have been studied under pseudo-first-order conditions in dioxane–water mixtures. It has been found that high solvent polarities and ionic strengths increase the reaction rate. The reaction is also promoted by electron-donating substituents (ρ–0.52). Strong acids have a catalytic effect on the reaction in which case the substituent effect is more pronounced (ρ–1.55). In neutral medium the deuterium solvent isotope effect is kH2O/kD2O 1.66, while in acidic medium the ratio of catalytic constants is found to be 0.56. The rate of the reaction is greatly increased with the increasing size of the spiroring (from 5 to 7) in the sulfurane. Kinetic data suggest a dissociative reaction mechanism.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"78 1","pages":"855-859"},"PeriodicalIF":0.0,"publicationDate":"2010-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91207654","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}
L. Brown, P. Halling, G. Johnston, C. Suckling, R. Valivety
A series of water insoluble dyes for the measurement of pH in an inaccessible water phase in water immiscible solvents have been designed and synthesised based upon the fluorescein system. The solubilities of the anionic forms of the dyes depend strongly upon the nature of the ester substituent and the degree of substitution of the aromatic rings. For dye molecules with long chain alkyl esters and with bromine substituents in the rings, the sodium or potassium salts are soluble in organic solvents such as diethyl ketone or ethyl acetate and the anions do not partition measurably into aqueous solution. Other less highly substituted dyes can be solubilised as their anions by the addition of quaternary ammonium salts or crown ethers. Titration curves for the dyes show that they are able to respond reproducibly to the pH of a water phase in contact with the organic phase although the detailed physical chemistry of the ion exchange is complex. Certain of the dyes are suitable for monitoring the pH in reaction systems using enzymes as catalysts in water immiscible solvents.
{"title":"The synthesis of some water insoluble dyes for the measurement of pH in water immiscible solvents","authors":"L. Brown, P. Halling, G. Johnston, C. Suckling, R. Valivety","doi":"10.1039/P19900003349","DOIUrl":"https://doi.org/10.1039/P19900003349","url":null,"abstract":"A series of water insoluble dyes for the measurement of pH in an inaccessible water phase in water immiscible solvents have been designed and synthesised based upon the fluorescein system. The solubilities of the anionic forms of the dyes depend strongly upon the nature of the ester substituent and the degree of substitution of the aromatic rings. For dye molecules with long chain alkyl esters and with bromine substituents in the rings, the sodium or potassium salts are soluble in organic solvents such as diethyl ketone or ethyl acetate and the anions do not partition measurably into aqueous solution. Other less highly substituted dyes can be solubilised as their anions by the addition of quaternary ammonium salts or crown ethers. Titration curves for the dyes show that they are able to respond reproducibly to the pH of a water phase in contact with the organic phase although the detailed physical chemistry of the ion exchange is complex. Certain of the dyes are suitable for monitoring the pH in reaction systems using enzymes as catalysts in water immiscible solvents.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"24 1","pages":"3349-3353"},"PeriodicalIF":0.0,"publicationDate":"2010-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76628393","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}
A quaternary carbon atom can be set up by irradiation of the N-methylaniline enamine 5 of adamantane-2-carbaldehyde giving the indoline 6 in poor yield. This product was converted into the spiro-oxindole 8, but only in very low yield. Quaternary carbon atoms can be set up more efficiently from the ketone group of adamantanone in two high-yielding steps by conjugate addition of appropriate organometallic carbon nucleophiles to the electrophilic alkenes 9 and 25, obtained by condensation of adamantanone with either Meldrum's acid or nitromethane. By use of the latter intermediate 25, a high yielding, eight-step conversion of adamantanone into the corresponding spiro-oxindole 8 can be carried out. Conjugate addition of triphenylaluminium to the corresponding nitroalkene 33 derived from 2-oxaadamantan-4-one 32 takes place with high stereoselectivity in the sense appropriate for a synthesis of gelsemine, with the phenyl group in the product 34cis to the oxygen bridge.
{"title":"A new oxindole synthesis","authors":"I. Fleming, R. Moses, M. Tercel, J. Ziv","doi":"10.1039/P19910000617","DOIUrl":"https://doi.org/10.1039/P19910000617","url":null,"abstract":"A quaternary carbon atom can be set up by irradiation of the N-methylaniline enamine 5 of adamantane-2-carbaldehyde giving the indoline 6 in poor yield. This product was converted into the spiro-oxindole 8, but only in very low yield. Quaternary carbon atoms can be set up more efficiently from the ketone group of adamantanone in two high-yielding steps by conjugate addition of appropriate organometallic carbon nucleophiles to the electrophilic alkenes 9 and 25, obtained by condensation of adamantanone with either Meldrum's acid or nitromethane. By use of the latter intermediate 25, a high yielding, eight-step conversion of adamantanone into the corresponding spiro-oxindole 8 can be carried out. Conjugate addition of triphenylaluminium to the corresponding nitroalkene 33 derived from 2-oxaadamantan-4-one 32 takes place with high stereoselectivity in the sense appropriate for a synthesis of gelsemine, with the phenyl group in the product 34cis to the oxygen bridge.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"41 1","pages":"617-626"},"PeriodicalIF":0.0,"publicationDate":"2010-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82355825","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}
C. O'Connor, W. Denny, Junjie Fan, G. L. Gravatt, B. A. Grigor, D. J. Mclennan
Rate constants for the hydrolysis of a series of aromatic nitrogen mustards Ar–X–C6H4-N(CH2CH2Cl)2(X = O, CH2, CONH, S, CO and SO2) in buffered aqueous acetone mixtures have been obtained using an HPLC technique which allows evaluation of the rate constants for hydrolytic displacement of both chlorines in consecutive reactions. Hydrolysis has a general-base-catalysed component and is accompanied by external chloride ion return. An aziridinium ion intermediate is implicated in at least one pathway. The mustards also alkylate the nucleophiles thiourea and 4-(4-nitrobenzyl)pyridine (NBP) and again the aziridinium ion intermediate is involved since the kinetic behaviour rules out a direct SN2 pathway.
用高效液相色谱法测定了一系列芳香族氮芥菜Ar-X-C6H4-N (CH2CH2Cl)2(X = O, CH2, CONH, S, CO和SO2)在缓冲丙酮水溶液中水解的速率常数，从而测定了两种氯在连续反应中的水解位移速率常数。水解具有一般碱催化成分，并伴有外部氯离子返回。氮铱离子中间体至少参与一种途径。芥菜还使亲核试剂硫脲和4-(4-硝基苄基)吡啶(NBP)烷基化，由于动力学行为排除了直接SN2途径，因此再次涉及氮鎓离子中间体。
{"title":"Hydrolysis and alkylating reactivity of aromatic nitrogen mustards","authors":"C. O'Connor, W. Denny, Junjie Fan, G. L. Gravatt, B. A. Grigor, D. J. Mclennan","doi":"10.1039/P29910001933","DOIUrl":"https://doi.org/10.1039/P29910001933","url":null,"abstract":"Rate constants for the hydrolysis of a series of aromatic nitrogen mustards Ar–X–C6H4-N(CH2CH2Cl)2(X = O, CH2, CONH, S, CO and SO2) in buffered aqueous acetone mixtures have been obtained using an HPLC technique which allows evaluation of the rate constants for hydrolytic displacement of both chlorines in consecutive reactions. Hydrolysis has a general-base-catalysed component and is accompanied by external chloride ion return. An aziridinium ion intermediate is implicated in at least one pathway. The mustards also alkylate the nucleophiles thiourea and 4-(4-nitrobenzyl)pyridine (NBP) and again the aziridinium ion intermediate is involved since the kinetic behaviour rules out a direct SN2 pathway.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"16 1","pages":"1933-1939"},"PeriodicalIF":0.0,"publicationDate":"2010-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83473832","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}
The electrochemical oxidation of adenine and hydroxyadenines has been studied in aqueous solutions in the pH range 3.0–11.2 using a pyrolytic graphite electrode. The initial course of the electrode reaction has been deduced to involve a 2e, 2H+ reaction to give 2- and not 8-hydroxyadenine, further oxidation of which gives 2,8-dihydroxyadenine and then diimine species which undergo a series of chemical reactions to give different products. The major products of oxidation at pH 3.0 {urea, alloxan [2,4,5,6(1H,3H)-pyrimidinetetrone] and parabanic acid (imidazolidinetrione)} and at pH 7.0 [allantoin (5-ureidohydantoin)] have been isolated using HPLC and column chromatography and their structures elucidated by spectroscopic techniques. The probable EC mechanisms for their formation have also been suggested.
{"title":"Oxidation chemistry of adenine and hydroxyadenines at pyrolytic graphite electrodes","authors":"R. Goyal, Anoop Kumar, A. Mittal","doi":"10.1039/P29910001369","DOIUrl":"https://doi.org/10.1039/P29910001369","url":null,"abstract":"The electrochemical oxidation of adenine and hydroxyadenines has been studied in aqueous solutions in the pH range 3.0–11.2 using a pyrolytic graphite electrode. The initial course of the electrode reaction has been deduced to involve a 2e, 2H+ reaction to give 2- and not 8-hydroxyadenine, further oxidation of which gives 2,8-dihydroxyadenine and then diimine species which undergo a series of chemical reactions to give different products. The major products of oxidation at pH 3.0 {urea, alloxan [2,4,5,6(1H,3H)-pyrimidinetetrone] and parabanic acid (imidazolidinetrione)} and at pH 7.0 [allantoin (5-ureidohydantoin)] have been isolated using HPLC and column chromatography and their structures elucidated by spectroscopic techniques. The probable EC mechanisms for their formation have also been suggested.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"67 1","pages":"1369-1375"},"PeriodicalIF":0.0,"publicationDate":"2010-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78743537","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}
The structure of LL-D253α, a Chromanone metabolite of Phoma pigmentivora has been revised by analysis of the 1H-coupled 13C NMR spectrum to 7-hydroxy-8-(2′-hydroxyethyl)-5-methoxy-2-rnethyl-chroman-4-one. This has been further established by the synthesis of the revised and previously proposed structures of LL-D253α.
{"title":"Structural revision and synthesis of LL-D253α and related chromanone fungal metabolites","authors":"I. M. Chandler, C. Mcintyre, T. J. Simpson","doi":"10.1039/P19920002271","DOIUrl":"https://doi.org/10.1039/P19920002271","url":null,"abstract":"The structure of LL-D253α, a Chromanone metabolite of Phoma pigmentivora has been revised by analysis of the 1H-coupled 13C NMR spectrum to 7-hydroxy-8-(2′-hydroxyethyl)-5-methoxy-2-rnethyl-chroman-4-one. This has been further established by the synthesis of the revised and previously proposed structures of LL-D253α.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"29 1","pages":"2271-2284"},"PeriodicalIF":0.0,"publicationDate":"2010-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86518847","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}
Qualitative symmetry arguments, evidence from bondlengths and energies, and from the addition chemistry of C60 point to a localised description of the π system of this molecule. Regioselective saturation of six double bonds in C60 is predicted to lead to an alternant delocalised (aromatic)π system that is realised in at least one well characterised compound.
{"title":"Is aromaticity a useful concept for C60 and its derivatives? Aromatisation of C60 by regioselective addition","authors":"P. Fowler, D. J. Collins, S. Austin","doi":"10.1039/P29930000275","DOIUrl":"https://doi.org/10.1039/P29930000275","url":null,"abstract":"Qualitative symmetry arguments, evidence from bondlengths and energies, and from the addition chemistry of C60 point to a localised description of the π system of this molecule. Regioselective saturation of six double bonds in C60 is predicted to lead to an alternant delocalised (aromatic)π system that is realised in at least one well characterised compound.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"63 1","pages":"275-277"},"PeriodicalIF":0.0,"publicationDate":"2010-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80965249","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}
H. Dharmaratne, J. Kilgore, E. Roitman, C. Shackleton, E. Caspi
The 16- 2H 2 title compound 5b constituted a significant amount of the non-aromatic metabolites recovered from incubations of 3,17-dioxo-[16,16,19- 2H 3]androst-4-en-19-al 1 with placental aromatase. For the evaluation of the role of compound 5b in the elaboration of estrogens, its transformations at pH 6.5 and 7.2 in the presence and absence of microsomal placental aromatase were investigated. In the presence of the aromatase at pH 6.5, estrogens (6.8%), products of isomerization of the double bond [Δ 5(10)→Δ 4] and products of reduction of the carbonyl groups were formed. When the incubation was carried out at pH 7.2, products similar to those obtained above were isolated but in different yields. Noticeably more estrogens (22.7%) and less of the reduced products were formed. Additionally, at pH 7.2, 10β-hydroxy-[16,16- 2H 2]estr-4-ene-3,17-dione 4a was obtained. In the absence of the aromatase, which was replaced with bovine albumin at both pH 6.5 and 7.2, [16,16- 2H 2]estr-4-ene-3,17-dione 3a and its 10β-hydroxy derivative 4a were formed in large amounts and were the only products detected. The ramifications of our observations in the context of estrogen biosynthesis are discussed.
{"title":"Biosynthesis of estrogens. Estr-5(10)-ene-3,17-dione: isolation, metabolism and mechanistic implications","authors":"H. Dharmaratne, J. Kilgore, E. Roitman, C. Shackleton, E. Caspi","doi":"10.1039/P19930001529","DOIUrl":"https://doi.org/10.1039/P19930001529","url":null,"abstract":"The 16- \u0000 2H \u0000 2 title compound \u0000 5b constituted a significant amount of the non-aromatic metabolites recovered from incubations of 3,17-dioxo-[16,16,19- \u0000 2H \u0000 3]androst-4-en-19-al 1 with placental aromatase. For the evaluation of the role of compound 5b in the elaboration of estrogens, its transformations at pH 6.5 and 7.2 in the presence and absence of microsomal placental aromatase were investigated. In the presence of the aromatase at pH 6.5, estrogens (6.8%), products of isomerization of the double bond [Δ \u0000 5(10)→Δ \u0000 4] and products of reduction of the carbonyl groups were formed. When the incubation was carried out at pH 7.2, products similar to those obtained above were isolated but in different yields. Noticeably more estrogens (22.7%) and less of the reduced products were formed. Additionally, at pH 7.2, 10β-hydroxy-[16,16- \u0000 2H \u0000 2]estr-4-ene-3,17-dione \u0000 4a was obtained. \u0000 \u0000 In the absence of the aromatase, which was replaced with bovine albumin at both pH 6.5 and 7.2, [16,16- \u0000 2H \u0000 2]estr-4-ene-3,17-dione \u0000 3a and its 10β-hydroxy derivative \u0000 4a were formed in large amounts and were the only products detected. \u0000 \u0000 The ramifications of our observations in the context of estrogen biosynthesis are discussed.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"2009 1","pages":"1529-1535"},"PeriodicalIF":0.0,"publicationDate":"2010-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82587447","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}
The important deshielding effect on the 17O signal of the disilyl ketone 1(Δδ ca. 400 ppm, compared with normal ketones such as 3) and of the monosilylketones 2, is proportional to the λ values of the UV–VIS absorption spectra; in agreement with the r-term of the Karplus–Pople eqn. (1), it is four times larger than the analogous effect on the 13C signals of the carbonyl carbon.
{"title":"NMR of terminal oxygen. Part 11. 17O NMR spectra of disilyl ketone and related compounds: a case of strong deshielding by electronic excitation energy","authors":"H. Dahn, P. Péchy, H. Bestmann","doi":"10.1039/P29930001497","DOIUrl":"https://doi.org/10.1039/P29930001497","url":null,"abstract":"The important deshielding effect on the 17O signal of the disilyl ketone 1(Δδ ca. 400 ppm, compared with normal ketones such as 3) and of the monosilylketones 2, is proportional to the λ values of the UV–VIS absorption spectra; in agreement with the r-term of the Karplus–Pople eqn. (1), it is four times larger than the analogous effect on the 13C signals of the carbonyl carbon.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"44 1","pages":"1497-1498"},"PeriodicalIF":0.0,"publicationDate":"2010-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76371184","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}
Accurate determinations have been made for the EPR coupling constants of 15 para-substituted benzyl radicals. These data, along with literature data for other systems have been used to reassess the stabilizing effect of para-substituents on benzylic radicals, and to throw light on the possible destabilizing effects of para F and CF3 substituents.
{"title":"Stabilization of benzylic radicals by substituents: an EPR study of para-substituted benzyl radicals","authors":"R. A. Jackson, M. Sharifi","doi":"10.1039/P29960000775","DOIUrl":"https://doi.org/10.1039/P29960000775","url":null,"abstract":"Accurate determinations have been made for the EPR coupling constants of 15 para-substituted benzyl radicals. These data, along with literature data for other systems have been used to reassess the stabilizing effect of para-substituents on benzylic radicals, and to throw light on the possible destabilizing effects of para F and CF3 substituents.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"23 1","pages":"775-778"},"PeriodicalIF":0.0,"publicationDate":"2010-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78062492","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}
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