摘要:
An efficient one-pot Erlenmeyer-Plochl reaction affords high yields of optically active aliphatic dehydroamino acid derivatives. Subsequent halogenation with NBS or NIS yields the alpha-halo-imine derivatives which undergo kinetically controlled tautomerization with Et3N, resulting in increased E selectivity. Isomerization of these derivatives in the presence of strong base (DABCO) results in exclusive formation of the more stable Z vinyl bromides. High yields of the beta-halo-dehydroamino acids are obtained in all cases.