Intramolecular hydride shift in some noncyclic isopropyl ketols

Abstract

The acyclic ketols [Formula: see text] have been synthesized by a Reformatsky sequence. Each ketol undergoes intramolecular hydride transfer when refluxed in KOH–H2O–t-BuOH solution. When the procedure was applied to the synthesis of 34, hydride transfer occurred during the Reformatsky reaction to yield 33 instead. With longer reaction times, 33 underwent self-acylation and β-dicarbonyl cleavage to 37. Treatment of 33 with aqueous base gave a mixture of ketols 35 and 36 from hydride transfer and β-keto decarboethoxylation. The attempted conversion of the isobutyrate group of the Reformatsky intermediates 21 and 24 to tert-butyl was not practicable.