Reactions of 2-(methylchalcogeno)phenylvinylketones 1 and 4 with aldehydes 5 were conducted in the presence of BF3·Et2O. The reaction was quenched by addition of Et3N 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 NaHCO3, the sulfonium salt 8a was obtained together with 6. Ketones 10, α-diketones, and α-oxo