Integrated Pd-catalyzed cross-coupling strategies for furnishing α-carbolines

Efficient synthetic strategies for furnishing alpha-carbolines have been developed by integrating various Pd-catalyzed reactions. The methods involve 1) regioselective 5- or 6-halogenation of alpha-carbolines which were synthesized through intramolecular Pd-catalyzed direct C-H arylation, and subsequent Pd-catalyzed cross coupling, 2) 8-triflation of alpha-carbolines constructed by Pd-catalyzed cyclization, followed by Pd-catalyzed cross-coupling reaction, 3) Pd-catalyzed cyclization to tetrahydro-alpha-carbolines and subsequent Suzuki reaction via the corresponding a-carboline 5-triflates. (C) 2017 Elsevier Ltd. All rights reserved.