Unprecedented dual reactivity of anhydrous potassium hydroxide in cascade cyclopropannelation/Haller-Bauer-scission/Grob-fragmentation reactions

Whereas potassium hydroxide reacts with a large variety of 2,2-dimethyl-substituted cyclohexanones bearing two leaving groups at 3,4-positions to produce vinyl lactones or/and their vinyl cyclopropane carboxylic acid isomers, 'anhydrous potassium hydroxide' (from 3/1 t-BuOK/H2O) exclusively produces the latter in very high yield under very mild conditions.