Cross-coupling reactions of indium organometallics with 2,5-dihalopyrimidines: synthesis of hyrtinadine A.

The palladium-catalyzed cross-coupling reaction of triorganoindium reagents (R₃In) with 5-bromo-2-chloropyrimidine proceeds chemoselectively, in good yields, to give 5-substituted-2-chloropyrimidines or 2,5-disubstituted pyrimidines using 40 or 100 mol% of R₃In, respectively. Sequential cross-couplings are also performed, in one pot, using two different R₃In. This method was used to achieve the first synthesis of the alkaloid hyrtinadine A. The key step was a two-fold cross-coupling reaction between a tri(3-indolyl)indium reagent and 5-bromo-2-chloropyrimidine.