Abstract
The synthetic utilities of conjugated oxime ethers as a radical acceptor are described. The triethylborane-mediated intermolecular carbon radical addition to chiral conjugated oxime ether proceeded regio- and stereoselectively. The radical reaction of conjugated oxime ether with triethylborane in the presence of aldehyde afforded γ-butyrolactone via sequential process involving ethyl radical addition, generation of N-boryl enamine, aldol-type reaction with aldehyde and lactonization. On the other hand, treatment of conjugated oxime ether with triethylborane and thiophenol in the presence of O2 gave β-hydroxysulfides with high regioselectivity and good yield. The reaction would proceed through radical pathway involving regioselective addition and the subsequent trapping of the resulting α-imino radical with O2, where the imino group enhances the stability of the intermediate radical. The hydroxyalkylation reaction via carbon radical addition and hydroxylation with O2 was also developed.
