(–)-Podophyllotoxin of 98% optical purity has been synthesized in eight steps and in 15% overall yield. The key step, Diels–Alder addition of the o-quinonoid pyrone 2 [6,7-methylenedioxy-1-(3,4,5-trimethoxyphenyl)-2-benzopyran-3-one] to the chiral dienophile 5 [5-(–)-menthyloxyfuran-2(5H)-one], proceeds with very high regio-, endo- and facial selectivity.
{"title":"Asymmetric total synthesis of (–)-podophyllotoxin","authors":"Edward J. Bush, David W. Jones","doi":"10.1039/P19960000151","DOIUrl":"https://doi.org/10.1039/P19960000151","url":null,"abstract":"(–)-Podophyllotoxin of 98% optical purity has been synthesized in eight steps and in 15% overall yield. The key step, Diels–Alder addition of the o-quinonoid pyrone 2 [6,7-methylenedioxy-1-(3,4,5-trimethoxyphenyl)-2-benzopyran-3-one] to the chiral dienophile 5 [5-(–)-menthyloxyfuran-2(5H)-one], proceeds with very high regio-, endo- and facial selectivity.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"7 1","pages":"151-155"},"PeriodicalIF":0.0,"publicationDate":"2010-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74415099","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. Medforth, C. Muzzi, K. Shea, Kevin M Smith, R. J. Abraham, S. Jia, J. Shelnutt
The ligand orientations in the nonplanar porphyrin complexes 1a–e and 2a–e have been investigated using molecular mechanics calculations and proton NMR spectroscopy. The minimum energy structures calculated for complexes 1a–e show that the planes of the axial pyridine or imidazole ligands are orientated approximately parallel to the CoIII–Nporphyrin bonds, with the ligand ring planes being perpendicular to each other. For complexes 2a–e, the planes of the axial ligands in the calculated minimum energy structures are orientated along the porphyrin meso carbon axis and the ligand ring planes are perpendicular to each other. Thus, for both series of complexes the planes of the axial ligands are orientated parallel to cavities formed by these very nonplanar porphyrins. Proton NMR studies suggest that structures similar to those obtained from the molecular mechanics calculations are retained in solution. In some complexes, hindered rotation of the axial ligands is also observed. Complexes 1a–e and 2a–e are unusual examples of the porphyrin conformation influencing the orientations of axial ligands and, as such, may be useful as models for studying ligand orientation effects in relation to biological systems.
{"title":"NMR STUDIES OF NONPLANAR PORPHYRINS. PART 1. AXIAL LIGAND ORIENTATIONS IN HIGHLY NONPLANAR PORPHYRINS","authors":"C. Medforth, C. Muzzi, K. Shea, Kevin M Smith, R. J. Abraham, S. Jia, J. Shelnutt","doi":"10.1039/A603412H","DOIUrl":"https://doi.org/10.1039/A603412H","url":null,"abstract":"The ligand orientations in the nonplanar porphyrin complexes \u00001a–e and 2a–e have been investigated using molecular \u0000mechanics calculations and proton NMR spectroscopy. The minimum energy \u0000structures calculated for complexes 1a–e show that the planes of \u0000the axial pyridine or imidazole ligands are orientated approximately \u0000parallel to the CoIII–Nporphyrin bonds, \u0000with the ligand ring planes being perpendicular to each other. For \u0000complexes 2a–e, the planes of the axial ligands in the calculated \u0000minimum energy structures are orientated along the porphyrin \u0000meso carbon axis and the ligand ring planes are \u0000perpendicular to each other. Thus, for both series of complexes the \u0000planes of the axial ligands are orientated parallel to cavities formed \u0000by these very nonplanar porphyrins. Proton NMR studies suggest that \u0000structures similar to those obtained from the molecular mechanics \u0000calculations are retained in solution. In some complexes, hindered \u0000rotation of the axial ligands is also observed. Complexes 1a–e and \u00002a–e are unusual examples of the porphyrin conformation \u0000influencing the orientations of axial ligands and, as such, may be \u0000useful as models for studying ligand orientation effects in relation to \u0000biological systems.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"11 1","pages":"833-838"},"PeriodicalIF":0.0,"publicationDate":"2010-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82398543","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}
This review covers the literature published during the period from October 1996 to October 1997, with an emphasis placed upon solid-phase small molecule synthesis, linkers and cleavage strategies.
{"title":"Recent developments in solid-phase organic synthesis","authors":"Richard C. D. Brown","doi":"10.1039/A805801F","DOIUrl":"https://doi.org/10.1039/A805801F","url":null,"abstract":"This review covers the literature published during the period from October 1996 to October 1997, with an emphasis placed upon solid-phase small molecule synthesis, linkers and cleavage strategies.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"42 1","pages":"3293-3320"},"PeriodicalIF":0.0,"publicationDate":"2010-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85823667","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}
{"title":"Saturated nitrogen heterocycles","authors":"A. Mitchinson, A. Nadin","doi":"10.1039/A803231I","DOIUrl":"https://doi.org/10.1039/A803231I","url":null,"abstract":"Reviewing the literature published in 1999. Continuing the coverage in J. Chem. Soc., Perkin Trans. 1, 1999, 2553.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"67 1","pages":"3493-3514"},"PeriodicalIF":0.0,"publicationDate":"2010-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83214703","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}
{"title":"Nitro and related compounds","authors":"Joseph P. Adams, David S. Box","doi":"10.1039/A801494I","DOIUrl":"https://doi.org/10.1039/A801494I","url":null,"abstract":"Covering: the literature published between April 1998 and January 2000. Previous review: J. Chem. Soc., Perkin Trans. 1, 1999, 749.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"7 1","pages":"749-764"},"PeriodicalIF":0.0,"publicationDate":"2010-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85436713","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}
One hundred and fifty four lines have been detected in 120 000 and 50 000 scan 13C NMR spectra of main and tail HPLC fractions, respectively, of [84]fullerene. Five minor isomers are deduced to be present (in ca. 25% and 40% overall yields in the main and tail cuts, respectively), as well as the two main isomers [D2(IV) and D2d(II), which are present in a ratio of ca. 2.25∶1]. A second D2 isomer, which calculations predict to be D2(III), is firmly established as one of the components, and the other isomers are indicated to be: D3d, D6h, Cs(IV), and either Cs(V) or C2(IV). The relative proportions of the isomers differ according to the HPLC fraction, and a partial elution order (Cosmosil Buckyprep/toluene) is D3d/Cs(IV) < D2(III)/D6h. The IR spectrum of [84]fullerene does not correlate well with theoretical predictions.
{"title":"The minor isomers and IR spectrum of [84]fullerene","authors":"A. G. Avent, D. Dubois, A. Pénicaud, R. Taylor","doi":"10.1039/A703697C","DOIUrl":"https://doi.org/10.1039/A703697C","url":null,"abstract":"One hundred and fifty four lines have been detected in 120 000 and 50 000 scan 13C NMR spectra of main and tail HPLC fractions, respectively, of [84]fullerene. Five minor isomers are deduced to be present (in ca. 25% and 40% overall yields in the main and tail cuts, respectively), as well as the two main isomers [D2(IV) and D2d(II), which are present in a ratio of ca. 2.25∶1]. A second D2 isomer, which calculations predict to be D2(III), is firmly established as one of the components, and the other isomers are indicated to be: D3d, D6h, Cs(IV), and either Cs(V) or C2(IV). The relative proportions of the isomers differ according to the HPLC fraction, and a partial elution order (Cosmosil Buckyprep/toluene) is D3d/Cs(IV) < D2(III)/D6h. The IR spectrum of [84]fullerene does not correlate well with theoretical predictions.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"17 1","pages":"1907-1910"},"PeriodicalIF":0.0,"publicationDate":"2010-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84436237","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 1H and 13C NMR spectra of a series of 1,3-di-tert-butyl-1,3-diazacyclohexanes 6, and of 1,5-diazabicyclo[3.2.1]octanes 7, have been investigated in an attempt to find evidence regarding a stereoelectronic interaction of the non-bonding electron pairs on nitrogen or of the C–N bonding electron pairs in the ring, with the axial and equatorial CH bonds of the α- or β-methylene groups. In 6, the orbital carrying the non-bonding electron pair lies antiperiplanar to the axial α-CH bond; a significant nN→σ*CH 3-orbital interaction (the anomeric effect) is sterically possible, and this shows up in the values of δH and of 1JCH. In 7, the doubly-occupied orbital is orientated gauche to both the axial and equatorial α-CH bonds, and no anomeric effect is apparent. In 7 however, in contrast to 6, the stereochemistry is appropriate for a W-plan nN→σ*CH 4-orbital interaction with the equatorial β-CH bond, and comparison of the NMR data of 6 and 7 suggests that such a homoanomeric effect may operate, though it is much weaker than in the analogous 1,3-dioxanes. No evidence could be found for a σCN→σ*CH 3-orbital interaction.
{"title":"NMR study of stereoelectronic anomeric and homoanomeric effects on the axial and equatorial CH bonds in 1,3-diazacyclohexanes and 1,5-diazabicyclo[3.2.1]octanes","authors":"J. Edgar Anderson, J. Cai, Alwyn G. Davies","doi":"10.1039/A705034H","DOIUrl":"https://doi.org/10.1039/A705034H","url":null,"abstract":"The 1H and 13C NMR spectra of a series of 1,3-di-tert-butyl-1,3-diazacyclohexanes 6, and of 1,5-diazabicyclo[3.2.1]octanes 7, have been investigated in an attempt to find evidence regarding a stereoelectronic interaction of the non-bonding electron pairs on nitrogen or of the C–N bonding electron pairs in the ring, with the axial and equatorial CH bonds of the α- or β-methylene groups. In 6, the orbital carrying the non-bonding electron pair lies antiperiplanar to the axial α-CH bond; a significant nN→σ*CH 3-orbital interaction (the anomeric effect) is sterically possible, and this shows up in the values of δH and of 1JCH. In 7, the doubly-occupied orbital is orientated gauche to both the axial and equatorial α-CH bonds, and no anomeric effect is apparent. In 7 however, in contrast to 6, the stereochemistry is appropriate for a W-plan nN→σ*CH 4-orbital interaction with the equatorial β-CH bond, and comparison of the NMR data of 6 and 7 suggests that such a homoanomeric effect may operate, though it is much weaker than in the analogous 1,3-dioxanes. No evidence could be found for a σCN→σ*CH 3-orbital interaction.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"329 1","pages":"2633-2638"},"PeriodicalIF":0.0,"publicationDate":"2010-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78429612","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 stereoselectivity of the hydrosilane reduction of substituted di(1-adamantyl)benzyl cations obtained by the protonation of aryldi(1-adamantyl)methanols by trifluoroacetic acid (TFA) in dichloromethane depends on both the hydrosilane and the substituent. Hydrosilanes react with meta-substituted (Me, But or CF3) phenyldi(1-adamantyl)methanols to give variable amounts of the anti and syn hydrocarbons, the variations being rather more pronounced for But (anti:syn = 0.7–23) than for Me (0.32–3.8) and CF3 (0.41–5.4). Almost all o-tolyldiadamantylmethanes give the anti isomer exclusively, as established by NMR spectroscopy and a single crystal X-ray diffraction study of the p-fluoro derivative. In the case of the [2-methyl-5-(tert-butyl)phenyl]diadamantylmethyl cation, however, the stereoselectivity and the rate of hydride transfer depend on the hydrosilane, the most encumbered giving hydrocarbon very slowly. Replacing the hydrosilane by sodium borohydride in these reactions results in untypical stereoselectivities. In particular, small yields of anti-(2-ethylphenyl)diadamantylmethane result from reduction of the corresponding alcohol, whereas normally only products with the syn conformation are obtained from this material.
{"title":"Steric effects in the ionic hydrogenation of aryldi(1-adamantyl)methanols to the corresponding methanes by trifluoroacetic acid and hydrosilanes or sodium borohydride","authors":"J. Lomas, J. Vaissermann","doi":"10.1039/A703648E","DOIUrl":"https://doi.org/10.1039/A703648E","url":null,"abstract":"The stereoselectivity of the hydrosilane reduction of substituted di(1-adamantyl)benzyl cations obtained by the protonation of aryldi(1-adamantyl)methanols by trifluoroacetic acid (TFA) in dichloromethane depends on both the hydrosilane and the substituent. Hydrosilanes react with meta-substituted (Me, But or CF3) phenyldi(1-adamantyl)methanols to give variable amounts of the anti and syn hydrocarbons, the variations being rather more pronounced for But (anti:syn = 0.7–23) than for Me (0.32–3.8) and CF3 (0.41–5.4). Almost all o-tolyldiadamantylmethanes give the anti isomer exclusively, as established by NMR spectroscopy and a single crystal X-ray diffraction study of the p-fluoro derivative. In the case of the [2-methyl-5-(tert-butyl)phenyl]diadamantylmethyl cation, however, the stereoselectivity and the rate of hydride transfer depend on the hydrosilane, the most encumbered giving hydrocarbon very slowly. Replacing the hydrosilane by sodium borohydride in these reactions results in untypical stereoselectivities. In particular, small yields of anti-(2-ethylphenyl)diadamantylmethane result from reduction of the corresponding alcohol, whereas normally only products with the syn conformation are obtained from this material.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"79 1","pages":"2589-2596"},"PeriodicalIF":0.0,"publicationDate":"2010-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90313011","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}
{"title":"AZULENE-ANNULATED TRICYCLO4.3.1.01,6DECA-2,4,7-TRIENE DERIVATIVES AND THEIR ANIONS. A NOVEL CYCLOHEPTATRIENE-NORCARADIENE VALENCE ISOMERIZATION IN THE AZULENE-ANNULATED TRICYCLO4.3.1.0.1,6DECA-2,4,7-TRIENE RING SYSTEM","authors":"M. Nitta, T. Takayasu","doi":"10.1002/CHIN.199835120","DOIUrl":"https://doi.org/10.1002/CHIN.199835120","url":null,"abstract":"","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"53 1","pages":"1325-1333"},"PeriodicalIF":0.0,"publicationDate":"2010-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82708906","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}
{"title":"Main group organometallics in synthesis","authors":"I. Coldham","doi":"10.1039/A706956A","DOIUrl":"https://doi.org/10.1039/A706956A","url":null,"abstract":"","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"33 1","pages":"1343-1364"},"PeriodicalIF":0.0,"publicationDate":"2010-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83176191","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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