LEWIS-ACID CATALYZED GEMINAL ACYLATION REACTION OF KETONES WITH 1,2-BIS((TRIMETHYLSILYL)OXY)CYCLOBUTENE - DIRECT FORMATION OF 2,2-DISUBSTITUTED 1,3-CYCLOPENTANEDIONES

Ketones reacted with 1,2-bis((trimethylsilyl)oxy)cyclobutene (1) under catalysis by boron trifluoride etherate to yield 2,2-disubstituted 1, 3-cyclopentanedione products via silylated cyclobutanone intermediates in a two-step, one-pot process. In many instances addition of a small amount of water to the reaction medium after completion of the first step assisted the subsequent rearrangement to the product, such that r eversion of the intermediate to the starting ketone became an insignif icant process. Yields were best with cyclohexanones (>90%), but steric hindrance and conjugated double bonds reduced yields considerably.