Phosphine-free thiopseudourea-Pd(II) complex catalyzed Larock heteroannulation of 2-haloamines with internal alkynes

We examined the Pd-catalyzed heteroannulation of 2-haloamines with internal alkynes under phosphine-free conditions. The thiopseudourea palladium(II) complex (5) found to be an efficient catalyst for the Pd induced heteroannulation. Achieved high turnover number for the heteroannulation reactions of internal alkynes with 2-iodoaniline. A variety of 2-bromoanilines and N-tosyl substituted 2-bromoanilines effectively reacted with different substituted internal alkynes to give the corresponding indoles in good to high yields (1:1 ratio of regioisomers).