Sulphur ylid prepn. from sulphonium salts - by reaction with inorganic base in organic solvent

摘要

Prepn. of S ylids of formula R1R2S=CZ1Z2 (I) is carried out by treating a sulphonium salt of formula. R1R2S(+)-CHZ1Z2.X-(II) with a base in a diluent at -10 to +80 deg.C, where the base is an alkali(ne earth) metal hydroxide, oxide, carbonate and/or alcoholate and the diluent is a 3-6C ketone, 3-5C alcohol and/or 4-8C ether (where R1 and R2 are alkyl or R1+R2 is a hydrocarbon chain opt. interrupted by heteroatoms; Z1 is CN, alkoxycarbonyl, CONH2, alkylcarbamoyl, alkanoyl or aroyl; Z2 is H, alkyl or as defined for Z1; X is halogen). (I) can be reacted with alkenes to form cyclopropane derivs., e.g. as intermediates for pyrethroid insecticides. The process gives high yields (e.g. 97-98%) in short reaction times using insoluble bases, which simplifies product work-up.