SYNTHESIS AND SYNTHETIC UTILIZATION OF ALPHA-FUNCTIONALIZED VINYLPHOSPHONATES BEARING BETA-OXY OR BETA-THIO SUBSTITUENTS

The beta-hetero-substituted vinylphosphonates la-e on treatment with L DA or LTMP were readily lithiated at the alpha-position of the phospho no group, and the resulting alpha-lithiovinylphosphonates were trapped with various electrophiles to afford the corresponding alpha-function alized vinylphosphonates 2-14 in 55-96% yields. The Friedel-Crafts rea ction of alpha-(silyl)- or alpha-(germyl)phosphonoketene dithioacetals 2, 9, or 4 with acid chlorides gave alpha-acylated phosphonoketene di thioacetals 15-19 in 53-91% yields. The palladium-catalyzed cross-coup ling reaction of eta-ethoxy-alpha-(tributylstannyl)vinylphosphonate 13 with a variety of organic halides (R = acyl, allyl, aryl, etc.) provi ded beta-ethoxy-alpha-substituted vinylphosphonates 21-26 in good to m oderate yields. The palladium-mediated cross-coupling reaction of alph a-(iodo)vinylphosphonates 7 and 14 with terminal acetylenes afforded a lpha-alkynylated vinylphosphonates 41-44 in 69-83% yields. Several alp ha-functionalized beta-hetero-substituted vinylphosphonates were. appl ied to the synthesis of pyrazoles and an isoxazole possessing a phosph ono function.