Chalcogeno Morita−Baylis−Hillman Reaction of 2‐(Methylchalcogeno)phenyl Vinyl Ketones with Aldehydes, Ketones, and α‐Dicarbonyl Compounds

Reactions of 2‐(methylchalcogeno)phenyl vinyl ketones 1 and 4 with aldehydes 5 were conducted in the presence of BF 3 ·Et 2 O. The reaction was quenched by addition of Et 3 N and gave the Morita−Baylis−Hillman adducts 6 − 7 in good yields. When the reaction mixture of 1 with 5a was worked up with saturated aqueous NaHCO 3 , the sulfonium salt 8a was obtained together with 6 . Ketones 10 , α‐diketones, and α‐oxo esters 13 , which hardly react in the traditional Morita−Baylis−Hillman reaction, similarly reacted with 2‐(methylchalcogeno)phenyl vinyl ketones 1 and 4 to give the Morita−Baylis−Hillman adducts 11 − 12 and 14 − 15 . Selenochromanones 9 and 16 were obtained together with 7 and 15 from reactions of seleno derivative 4 , with 5 and 13 as by‐products. The formation mechanism for the sulfonium salt syn ‐ trans ‐ 8a is discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)