Stereoselective synthesis of trans-olefins by the copper-mediated SN2′ reaction of vinyl oxazines with Grignard reagents. Asymmetric synthesis of d-threo-sphingosines

The SN2′ reaction of 6-vinyl-5,6-dihydro-4H-[1,3]oxazines with Grignard reagents in the presence of CuCN was studied, and high trans selectivity for the formation of double bond was observed with a variety of RMgX. The SN2′ reaction, coupled with regioselective asymmetric aminohydroxylation reaction, provided a highly efficient route for the asymmetric synthesis of d-threo-N-acetylsphingosine.