Abstract
A novel and efficient 4-step synthesis of 2,4-diamino-4-bromo-pyridine 4 in 56% overall yield by a double Curtius rearrangement as a key step is reported. N-amination of 2,4-diamino-4-bromo-pyridine 4 with O-mesitylenesulfonylhydroxylamine 10 and subsequent reaction with aldehydes yielded, upon oxidative ring-closure, 5-bromo-triazolopyridines 2a-2f. Thereafter, from a combinatorial parallel Suzuki cross-coupling reaction 260 previously non-described 5-aryl-[1,2,4]-triazolo-[1,5-a]-pyridines 1 were obtained in acceptable overall yield.

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