Synthesis and Synthetic Utilization of α-Functionalized Vinylphosphonates Bearing β-Oxy or β-Thio Substituents

Article abstract of DOI:10.1021/jo980467g

The β-hetero-substituted vinylphosphonates la-c on treatment with LDA or LTMP were readily lithiated at the α-position of the phosphono group, and the resulting α-lithiovinylphosphonates were trapped with various electrophiles to afford the corresponding α-functionalized vinylphosphonates 2-14 in 55-96% yields. The Friedel-Crafts reaction of α-(silyl)- or a-(germyl)-phosphonoketene dithioacetals 2, 9, or 4 with acid chlorides gave α-acylated phosphonoketene dithioacetals 15-19 in 53-91% yields. The palladium-catalyzed cross-coupling reaction of β-ethoxy-α-(tributylstannyl)vinylphosphonate 13 with a variety of organic halides (R = acyl, allyl, aryl, etc.) provided β-ethoxy-α-substituted vinylphosphonates 21-26 in good to moderate yields. The palladium-mediated cross-coupling reaction of α-(iodo)vinylphosphonates 7 and 14 with terminal acetylenes afforded α-alkynylated vinylphosphonates 41-44 in 69-83% yields. Several α-functionalized β-hetero-substituted vinylphosphonates were applied to the synthesis of pyrazoles and an isoxazole possessing a phosphono function.