Regiospecific Allylic Mono- and Dibromination of 4-Methoxy-1,1,1-trihalo-3-alken-2-ones and 5-Methoxy-1,1,1,2,2-pentafluoro-4-hexen-2-one, and their Applications to the Synthesis of Heterocycles

Abstract

A series of twelve 5-bromo[5,5-dibromo]-4-methoxy-1,1,1-trihalo-3-alken-2-ones 5a-d, 6a-d, 7a, 9a, 10a and 6-bromo-5-methoxy-1,1,1,2,2-pentafluoro-4-hexen-2-one (8a) were synthesized in high purity and good yields (70-95%) by the regiospecific allylic bromination of 4-methoxy-1,1,1-trihalo-3-alken-2-ones 1a-d, 2a-d, 3a or 5-methoxy-1,1,1,2,2-pentafluoro-4-hexen-2-one (4a), respectively, with bromine followed by addition of pyridine. The usefulness of compounds 5-10 in heterocyclic synthesis is also reported.