Synthesis and hetero-Diels-Alder reactions of (E)-alpha-perfluoroalkanesulfonyl-alpha,beta-unsaturated ketones

Catalyzed by ammonium acetate, the Knoevenagel reactions of beta-keto perfluoroalkanesulfones 1 with aromatic aldehydes 2 afforded alpha-perfluoroalkanesulfonyl-alpha,beta-unsaturated ketones 4 in moderate to good yields. The possible mechanism for the reactions was proposed. These fluorine-containing alpha,beta-unsaturated ketones, which are electron-poor 1-oxa-1,3-butadienes, could be used in inverse electron demand hetero Diels-Alder (HDA) reaction with electron-rich olefins to give tetrasubstituted dihydropyrans 6 in quantitative yields. (c) 2006 Elsevier Ltd. All rights reserved.