Darstellung von Didehydropyridinen aus (Trimethylsilyl)pyridinen

Publisher Website
Google Scholar
Abstract
Preparation of Didehydropyridines from (Trimethylsilyl)pyridinesHalogen‐substituted (trimethylsilyl)pyridines 2, 3, 5 – 7 and trifluoromethylsulfonyloxy‐substituted (trimethylsilyl)pyridines 9b, 11b are obtained from 2‐ and 3‐halopyridines 1, 4 or hydroxypyridines 8, 10, and 12. Reactions of the 3‐ and 2‐(trimethylsilyl)pyridines 2,9b and 11b with bases in the presence of furans 15 give only protodesilylation or hydrolysis products but no indication is found for the formation of a 2,3‐didehydropyridine. 3‐Bromo‐4‐(trimethylsilyl)pyridine (5a) reacts with KOCMe3 in the presence of furan (15a) to give a mixture of products from which the isoquinoline derivative 20 and the tert‐butoxypyridines 23, 24 are formed by addition to 3,4‐didehydropyridine. Under comparable conditions far higher yields of 3,4‐didehydropyridines are obtained by treatment of the 3‐halo‐2,4‐bis(trimethylsilyl)pyridines 7 with strong bases.