Synthesis of Dihydroquinolines via Pd/Cu-Catalyzed Heteroannulation

Significance

Reported is the synthesis of 3-bromodihydroquinolines via the Pd/Cu-catalyzed ­cyclization of N-propargyl anilines. Increasing bromide concentration through the addition of lithium bromide led to both increases in the yield and the rate of the reaction. Use of excess (>1 equiv) lithium bromide afforded the bis-brominated alkene 1. Treatment with ethanolic base led to aromatization by desulfonylation. The modest initial substrate scope established in this report includes limited cases of substituted alkynes. Confirmation of the structure of the product was achieved by X-ray crystallographic methods.