Efficient synthesis of new phosphono-substituted dihydrothiopyrans via hetero Diels-Alder reaction, under thermal and high pressure conditions

Article abstract of DOI:10.1016/S0040-4020(00)00297-0

New α-phosphono-β-aryl- or β-heteroaryl-substituted α,β-unsaturated dithioesters 2 were easily prepared from diethyl phosphonodithioacetate 1 and used as thiadienes in thermal or high pressure hetero Diels-Alder cycloadditions with enol and thioenol ethers. The resulting new phosphono 3,4-dihydro 2H-thiopyrans 3 were isolated in excellent yields and with a cis- or trans-diastereoselectivity depending on the conditions of the reaction as well as the structure of the reagents. Some of the thiopyrans 3 were also favourably synthesized via a domino Knoevenagel-hetero Diels-Alder sequence. (C) 2000 Elsevier Science Ltd.