Dimethyl sulfide-boron trihalide-mediated reactions of alpha,beta-unsaturated ketones with aldehydes: one-pot synthesis of Baylis-Hilman adducts and alpha-halomethyl enones

The reactions of aldehydes with 3-buten-2-one (2) were conducted in the pre sence of (BBr3Me2S)-Me-. or BCl3-Me2S and then worked up with aqueous NaHCO 3, affording the a-methylene aldol 3, (alpha -halomethyl aldol 4 or 6, and a-halomethyl enones 5 or 7, respectively. In contrast, the reactions quench ed with water gave the alpha -halomethyl enones 5 or 7 in high yields, whil e the work-up with an aqueous 10% trimethylamine gave the alpha -methylene aldol 3. The phenol 15 and half-acetal 16 were obtained from the reaction o f p-nitrobenzaldehyde (1a) with cyclohexenone (10). (C) 2001 Elsevier Scien ce Ltd. All rights reserved.