Enantioselective Addition of Nitrones to Activated Cyclopropanes
journal contributionposted on 27.04.2005, 00:00 by Mukund P. Sibi, Zhihua Ma, Craig P. Jasperse
In this paper, we demonstrate the first examples of chiral Lewis acid catalysis in the formation of tetrahydro-1,2-oxazines with very high enantioselectivity starting with diactivated cyclopropanes and nitrones (>90% yields and ee). Reactions with racemic substituted cyclopropanes provide ∼1:1 diastereomeric tetrahydro-1,2-oxazine products with high enantioselectivity. Mechanistic information for the formation of the tetrahydro-1,2-oxazines is also detailed.