Regioselective Synthesis of 2‐Trimethylsilyl‐4H‐pyran‐4‐ones from 1‐Ethoxy(hydroxy)‐5‐(trimethylsilyl)pentenynones

Abstract

AbstractExclusive formation of 5‐aryl‐2‐trimethylsilyl‐4H‐pyran‐4‐ones is accomplished by a regioselective cyclization of 2‐aryl‐1‐ethoxy(hydroxy)‐5‐(trimethylsilyl)pent‐1‐en‐4‐yn‐3‐ones. This cyclization occurs in a 6‐endo‐dig mode through addition to the β‐atom of the TMS substituted triple bond. The reaction was found to be general for a range of ethoxyenynones upon heating in glacial acetic acid and for analogous hydroxyenynones in diphenyl ether. Plausible mechanistic explanation and possible post‐modifications of resulting pyranones are offered.