Phosphonoketene dithioacetals 3a-e were obtained in good yields by the reaction of ethyl phosphonoacetates 1a,b with 2-4 equiv of thiols 2a-c in the presence of an alkylaluminum dichloride or dialkylaluminum chlorides. Reaction of 2,2-dithio-1-phosphonovinyl anions with aldehydes afforded allylic alcohols 4-7, 11-18 in good to moderate yields. Treatment of the alcohols 4-6 with t-BuOK in THF led to symmetrical [2 + 2] cycloadducts 20-22 of 1,1-(ethylenedithio)allenes in moderate yields, while a similar reaction of the alcohols 11-13 produced a mixture of symmetrical and unsymmetrical [2 + 2] cycloadducts of 1,1-(trimethylenedithio)allenes,23a-25a and 23b-25b, in 55-94% yields. The alcohol 15 on a similar treatment gave 3-tert-butyl-1,1-bis(ethylthio)allene (26) in quantitative yield. The structures of 20 and 23b were determined by X-ray analysis. Treatment of the alcohols 15 and 18 with trifluoromethanesulfonic acid/n-Bu(4)NX (X = Br, I) or triphenylphosphine/CBr(4) in CH(2)Cl(2) afforded alpha-phosphonodithioacryclic acid esters 34 and 35 in 25-52% yields. The tandem Michael-Wittig reaction of 35 with sodium salt of 2-pyrrolecarbaldehyde in DMF gave ethyl 3-phenyl-3H-cyclopenta[a]pyrrole-2-dithiocarboxylate (36) in 25% yield.

Synthesis and Synthetic Application of Phosphonoketene Dithioacetals. New Synthesis of Dithioallenes and (α-Dithiocarboxyvinyl) phosphonates. -Phosphonoketene dithioacetals such as (III) and (X) are prepared in high yields using organoaluminum chlorides. The anions of (III) and (X) are reacted with aldehydes to provide the allylic alcohols (V) and ( XII). The former react via dithioallenes to give (VI)-(VIII). The transformation of the dithioacetals (XII) to the α-phosphonodithioacrylic acid esters (XIII) and (XIV) is performed in the presence of a strong acid or under neutral conditions. -(MINAMI, T.; OKAUCHI, T.; MATSUKI, H.; NAKAMURA, M.; ICHIKAWA, J.; ISHIDA, M.; J.