C-Quaternary Vinylglycinols by Metal-Catalyzed Cyclization of Allylic Bistrichloroacetimidates

Bistrichloroacetimidates derived from 2-substituted but-2-ene-1,4-diols are transformed into 4-substituted 4-vinyloxazolines in high yields and excellent regioselectivities when Lewis acids AlCl3, FeCl3, TMSOTf, BF3 center dot OEt2, and AgBF4 are used as catalysts as well as with the Pd(PPh3)(2)Cl-2/AgBF4 catalytic system. Lower regioselectivity is achieved with a neutral PdCl2(MeCN)(2) catalyst and this could be a consequence of a switch to a competitive but less selective reaction mechanism. It is demonstrated that 4-substituted 4-vinyloxazolines can be efficiently transformed to N-Boc-protected C-quaternary vinylglycinols in a one-pot procedure.