Solvent- and structure-dependent regioselectivity in the boron-mediated aldol reaction of 2-(1,3-dioxolan-2-yl)ethyl ethyl ketones

The regioselectivity of the Chx(2)BCl/Et3N-mediated (Chx = cyclohexyl) aldol reactions of ketones of general structure 2 has been studied and was shown to depend on both ketone structure and solvent. Useful levels of regioselectivity in favour of any of the two possible regioisomers were obtained in either pentane or diethyl ether. The relative configuration of the aldol products was assigned by H-1 NMR studies of six-membered-ring derivatives. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).