Trimethylsilyl triflate catalysed Diels-Alder reaction of TMS ethers of conjugated dienols with cyclic enones: Evidence for an endo transition state, and first application to synthesis of enantiopure octalins
作者:Richard K. Haynes、Kwok-Ping Lam、Kit-Ying Wu、Ian D. Williams、Lam-Lung Yeung
DOI:10.1016/s0040-4020(98)01020-5
日期:1999.1
adduct acetal, whose controlled hydrolysis gives the hemiacetal with an α-axial methyl group. The adduct is thereby differentiated from the AlCl3 DA adduct, and may be converted into the latter by treatment with p-toluenesulfonic acid in aqueous THF or by AlCl3 in dichloromethane. In similar fashion, TMSOTf provides full acetal adducts from 2-cyclohexenone, 2-cycloheptenone and methyl vinyl ketone. The
AlCl 3在二氯甲烷中催化6-甲基-2-环己烯酮与3,5-己二烯-1-醇的“离子” Diels-Alder(DA)反应,得到具有β-赤道甲基和轴向羟基。相反,在-20℃下于乙腈中的三氟甲磺酸三甲基甲硅烷基酯(TMSOTf,5mol%)催化DA反应以产生反式-熔合加合物缩醛,其受控水解产生具有α-轴甲基的半缩醛。由此使该加合物与AlCl 3 DA加合物区别开,并且可以通过在THF水溶液中用对甲苯磺酸或通过AlCl 3处理将其转化为后者。在二氯甲烷中。TMSOTf以类似的方式提供了由2-环己烯酮,2-环庚烯酮和甲基乙烯基酮组成的全缩醛加合物。衍生自(1 R,2 R)-1,2-二苯基-1,2-乙二醇和2-环己烯酮的旋光烯酮缩醛得到衍生自己二烯醇的TMS醚的外消旋缩醛加合物。在-20°C下,在含有TMSOTf(10 mol%)的乙腈中,富含(2 R,5 E)-2-甲基-3,5-庚二烯-1-醇的3