Synthesis and application of easily recyclable thiomorpholines for use in sulfur ylide mediated asymmetric epoxidation of aldehydes

Chiral nonracemic thiomorpholines have been synthesized in four to six steps from limonene or achiral alkenes using alpha-methylbenzylamine to control absolute stereochemistry. These aminosulfides have been used to generate sulfur ylides, which have been applied in the asymmetric epoxidation of aldehydes as easily recoverable catalysts. Excellent yields (up to 98%), enantioselectivities (up to 97:3 e.r.), and diastercoselectivities (>= 98:2 trans/cis) were achieved in these epoxidations and the sulfides were easily recovered in high yield (up to 97%) by simple acid/base extraction.