Db. Berkowitz et al., SYNTHESIS OF HIGHER ALPHA-CHLOROVINYL AND ALPHA-BROMOVINYL AMINO-ACIDS - THE AMINO PROTECTING GROUP DETERMINES THE REACTION COURSE, Tetrahedron letters, 37(25), 1996, pp. 4309-4312
N-Trifluoroacetyl alpha-vinyl amino esters are smoothly converted to t
he corresponding alpha-chlorovinyl or alpha-bromovinyl amino esters th
rough the agency of phenyselenyl chloride or phenylselenyl bromide, re
spectively, followed by oxidation and pyrolysis. Exclusively the (E)-e
xternal halovinyl isomer and the internal halovinyl isomer am observed
. The amino protecting group is a critical determinant of the reaction
course (alkene addition vs. 5-exo-trig-like cyclization). Copyright (
C) 1996 Elsevier Science Ltd.