Intramolecular Diels–Alder additions to 2-benzopyran-3-ones; endo-selective additions and some reactions of the adducts
作者:David W. Jones、Firstborn Matthew Nongrum
DOI:10.1039/p19960000705
日期:——
system e.g. 18a (n= 3 or 4), the 2-benzopyran-3-ones 10a, 10b and 10c undergo endo-selective intramolecular Diels–Alder addition of the connecting chain to give cis-BC fused ring systems of type 13. The adduct 13b is converted into the ester 21 with methanolic HCl and into the ketol 36 by LiAlH4 reduction followed by oxidation (MnO2). The ketone 31 is prepared from 21 by epoxidation followed by BF3·Et2O-catalysed
Intramolecular Diels–Alder additions to 2-benzopyran-3-ones; anti-selectivity induced by the phenylsulfonyl group
作者:Edward J. Bush、David W. Jones、Firstborn Matthew Nongrum
DOI:10.1039/c39940002145
日期:——
The 2-benzopyran-3-ones 7a and 7c undergo intramolecularDiels–Alderaddition, via preferred endo-addition of the connecting chain, whereas for 7d and 7e(X = SO2Ph), exo-addition of the chain is preferred; the main adducts from the latter additions (9d and 9e), give the diterpene-related products 12(R = H, Y = OMe) and 12(R = Me, Y = OMe) upon treatment with sodium amalgam.
Intramolecular Diels–Alder additions to 2-benzopyran-3-ones; anti-selectivity induced by the phenylsulfonyl group 1
作者:Edward J. Bush、David W. Jones、Tracie C. L. M. Ryder
DOI:10.1039/a701589e
日期:——
Intramolecular DielsâAlder additions of the
2-benzopyran-3-ones 2d, 2e and 2f with an
E-SO2Ph substituent on the
dienophile (X = SO2Ph in 2) show greatly
enhanced exo-addition of the tether than is shown in the
absence of the E-SO2Ph group (X = H in
2). For 2e and 2f, exo-chain addition becomes preferred, and
for 2d, endo-chain addition much less preferred, than in
related cases with X = H. An E-CO2Me
group on the dienophile is also effective in enhancing
exo-chain addition, but less effective than an
E-SO2Ph group. The adducts 4e and 4f undergo
reductive elimination (5% NaâHg) to give the diterpene related
products 32 and 33 respectively.
2-苯并吡喃-3-酮 2d、2e 和 2f 的分子内 Diels–Alder 反应与具有 E-SO2Ph 替代基的二烯亲体(2 中 X = SO2Ph)相比,在没有 E-SO2Ph 基团(2 中 X = H)的情况下,连接的外加成反应显著增强。对于 2e 和 2f,外链加成变得更加优先,而对于 2d,内链加成相较于相关情况(X = H)则不那么优先。二烯亲体上的 E-CO2Me 基团在增强外链加成方面也有效,但效果不及 E-SO2Ph 基团。加成物 4e 和 4f 经过还原消除(5% Na–Hg)分别生成与二萜相关的产物 32 和 33。