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。