Pyrano- and Oxepinopyridines by RCM

Significance

Reported is a facile, high-yielding RCM route to 2H-dihydropyrano- and 2,3H-dihydro­oxepino[3,2-b]pyridines utilizing either Grubbs’ first- or second-generation catalyst. High catalyst loading is required suggesting that pyri­dines inhibit RCM processes. 3-Alkenyloxy-2-vinyl­pyridines are quickly accessed via commercially available 2-bromo-3-hydoxypyridine by a two-step Stille cross-coupling-O-alkylation protocol in 62-64% overall yields. The absence of developmental scope is superceded by the lack of effective preparations of the titled pyranopyridine system and the fact that the oxepinopyridine is unknown.