Palladium-Catalyzed Amino-Heck Reaction of γ,δ-Unsaturated Ketone <i>O</i>-Diethylphosphinyloximes: A New Synthesis of Substituted Pyrroles and Indoles
作者:Jia-Liang Zhu*、Yu-Hui Chan
DOI:10.1055/s-2008-1072728
日期:2008.5
starting materials for the intramolecular amino-Heck reactions. In the presence of a catalytic amount of Pd(PPh 3 ) 4 in DBU, cyclization reactions occurred preferentially via a 5- EXO fashion to afford a variety of 2-substituted 5-methyl-1 H-pyrroles and several indolederivatives in moderate to high yields.
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.