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Paper | Regular issue | Vol 71, No. 2, 2007, pp.361-371
Published online, 12th January, 2007
DOI: 10.3987/COM-06-10966
Lewis Acid-Catalyzed Michael Addition Reactions of N-Boc-2-silyloxypyrroles to 3-Acryloyl-2-oxazolidinone

Hiroyuki Suga,* Haruka Takemoto, and Akikazu Kakehi

*Department of Chemistry and Material Engineering, Faculty of Engineering, 4-17-1 Wakasato, Nagano 380-8553, Japan

Abstract

Among several Lewis acids examined, Sc(OTf)3 (10 mol%) was found to be the most effective catalyst to promote a Michael addition reaction of N-Boc-2-(tert-butyldimethylsilyloxy)pyrrole to 3-acryloyl-2-oxazolidinone. A slow addition of the 2-silyloxypyrrole in the presence of 1,1,1,3,3,3-hexafluoro-2-propanol (5 equiv.) at -25 °C were needed to obtain good yield (77 - 80%). The asymmetric version of the reaction could be performed with good enantioselectivity (up to 82% ee) by using the chiral Sc(III) catalyst (10 mol%), which was prepared from 2,6-bis[(4S)-4-isopropyl-2-oxazolin-2-yl]pyridine and Sc(OTf)3, in reasonable yield (60 - 70%).