jo960194u_si_001.pdf (1.33 MB)

Asymmetric [2 + 1] Cycloaddition Reactions of 1-Seleno-2-silylethene

Download (1.33 MB)
journal contribution
posted on 14.06.1996, 00:00 by Shoko Yamazaki, Mayumi Tanaka, Shinichi Yamabe
The reaction of (E)-1-(phenylseleno)-2-(trimethylsilyl)ethene (1) and vinyl ketones 2ad in the presence of a chiral Lewis acid prepared from TiCl4, Ti(OiPr)4, (R)- or (S)-1,1‘-binaphthol (BINOL), and MS4A gave enantiomerically enriched cis cyclopropane products 3ad. The enantiomeric excess and chemical yield varied depending on the ratio of TiCl4 and Ti(OiPr)4 to 1. Reproducible results (43−47% ee/33−41% yields) for cis-1-acetyl-2-[(phenylseleno)(trimethylsilyl)methyl]cyclopropane (3a) were obtained using 1.1 equiv of TiCl4, 0.54−0.65 equiv of Ti(OiPr)4, and 1.65 equiv of BINOL. The observed enantioselectivity was explained by consideration of the structure of the postulated intermediates, alkoxy titanium−carbonyl complexes, via ab initio MO calculations.