STUDIES ON THE AMINO-HECK REACTIONS OF UNSATURATED KETONES O-PHOSPHINYLOXIMES FOR THE PREPARATION OF SUBSTITUTED PYRIDINES

The amino-Heck cyclization process has been applied into a range of gamma,delta-unsaturated ketone O-diethylphosphinyloximes 1 and delta,epsilon-unsaturated ketone O-diethylphosphinyloximes 7. Under the specific catalytic conditions developed by us, these substrates were found to preferentially undergo the 6-endo cyclization to give the formation of 2-substituted pyridines 3 and substituted methylpyridines 8, respectively, in moderate to good yields. Besides, several interesting aspects on the effects of phosphinyl groups, solvents, bases and molecular sieves on the regioselectivity of the cyclization of 1 have also been realized.