1,2-Diarylethanols by Alternative Regioselective Reductive Ring-Opening of 2,3-Diaryloxiranes
作者:Nadia Di Blasio、Maria Teresa Lopardo、Paolo Lupattelli
DOI:10.1002/ejoc.200800992
日期:2009.2
Non-symmetrical trans-2,3-diaryloxiranes have been regioselectively opened by catalytic hydrogenation over Pd/C, NaBH4/Pd and [Cp2TiCl]/H2O. Although in the catalytic hydrogenation reactions the epoxides were mainly opened at the β-carbon with respect to the substituted aryl ring in all cases, with the [Cp2TiCl]/H2O system the regioselectivity was affected by the electronic properties of the aryl residues
非对称反式-2,3-二芳基环氧乙烷通过在 Pd/C、NaBH4/Pd 和 [Cp2TiCl]/H2O 上的催化氢化而被区域选择性地打开。尽管在催化加氢反应中,环氧化物主要在取代芳环的 β-碳处开环,但在 [Cp2TiCl]/H2O 体系中,区域选择性受芳基残基电子性质的影响,环氧化物在带有最多电子释放或最少吸电子基团的碳上打开。使用 NaBH4/Pd 系统,根据取代基获得不同的区域异构体。从对映体富集的环氧化物开始,在形成的醇中没有观察到光学纯度的损失。 (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)