Division of Organic Chemistry, Indian Institute of Chemical Technology, Hyderabad 500 007, India.
J Org Chem. 2011 Oct 7;76(19):7677-90. doi: 10.1021/jo201027u. Epub 2011 Sep 12.
Homoallylic substrates such as (E)-6-arylhex-3-enyl alcohols, N-tosylamides, and thiols undergo smooth cross-coupling with various aldehydes in the presence of 10 mol % Sc(OTf)(3) and 30 mol % TsOH to afford the trans-fused hexahydro-1H-benzo[f]isochromenes, N-tosyloctahydrobenzo[f]isoquinolines, and hexahydro-1H-benzo[f]isothiochromenes, respectively. However, the cross-coupling of (Z)-olefins such as 6-arylhex-3-enyl alcohols, N-tosylamides, and thiols with aldehydes affords the corresponding hexahydro-1H-benzo[f]isochromenes, N-tosyloctahydrobenzo[f]isoquinolines, and hexahydro-1H-benzo[f]isothiochromenes with complete cis selectivity via intramolecular Prins-, aza-Prins-, and thia-Prins/Friedel-Crafts cyclizations, respectively. Though the Prins cyclization proceeds smoothly under the influence of Sc(OTf)(3), high conversions and enhanced reaction rates are achieved using a mixture of Sc(OTf)(3) and TsOH (1:3).
(E)-6-芳基己-3-烯醇、N-对甲苯磺酰胺和硫醇等偕丙基底物在 10 mol% Sc(OTf)3 和 30 mol% TsOH 的存在下与各种醛顺利交叉偶联，分别得到反式稠合六氢-1H-苯并[f]异喹啉、N-对甲苯磺酰基-八氢苯并[f]异喹啉和六氢-1H-苯并[f]异硫代色烯。然而，(Z)-烯烃如 6-芳基己-3-烯醇、N-对甲苯磺酰胺和硫醇与醛的交叉偶联通过分子内 Prins、aza-Prins 和 thia-Prins/Friedel-Crafts 环化反应，分别以完全顺式选择性得到相应的六氢-1H-苯并[f]异喹啉、N-对甲苯磺酰基-八氢苯并[f]异喹啉和六氢-1H-苯并[f]异硫代色烯。尽管 Prins 环化在 Sc(OTf)3 的影响下顺利进行，但使用 Sc(OTf)3 和 TsOH（1:3）的混合物可实现高转化率和增强的反应速率。
