C-Quaternary Vinylglycinols by Metal-Catalyzed Cyclization of Allylic Bistrichloroacetimidates
19 October 2011 (eFirst)
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˙OEt2, and AgBF4 are used as catalysts as well as with the Pd(PPh3)2Cl2/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.
amino alcohols - Lewis acids - palladium - cyclization - regioselectivity