A General Entry to 10-Halocolchicides and 9-Haloisocolchicides

Abstract

Readily accessible 10-tosyloxycolchicide (1) and LiX (X=Cl or Br or I) in MeOH/BF₃Et₂O at reflux give 10-chloro- (2), 10-bromo- (4), or 10-iodocolchicide (5), in good yields. 9-Chloro- (7) and 9-bromoisocolchidide (8) can be similarly obtained from 9-tosyloxyisocolchidide (6) and the method applies also to troponoids.