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.
本研究以双 Curtius 重排为关键步骤,通过新颖高效的 4 步合成法合成了 2,4-二
氨基-4-
溴吡啶 4,总收率为 56%。将 2,4-二
氨基-4-
溴吡啶 4 与 O-甲磺酰
羟胺 10 进行 N-
氨基反应,随后与醛反应,氧化闭环后得到 5-
溴三唑并
吡啶 2a-2f。此后,通过组合平行铃木交叉偶联反应,以可接受的总收率得到了 260 个以前未曾描述过的 5-芳基-[1,2,4]-三唑并-[1,5-a]-
吡啶 1。