β-Oxidophosphonium ylides as nucleophiles react readily with various perhalalkanes via halophilic attack on C—X(X=I,Br or Cl) bonds to forma α-halosubstituted betaine intermediates, which can be transformed in situ into Z-isomers of chloro-, bromo- or iodo- substituted olefins as major products in good yields. These novel reactiosn may afford a facile route to various trisubsituted halo olefins by means of β-Oxidophosphonium ylides prepared in situ from various phosphonium salts and aldehydes.

Key words: HALOHYDROCARBON, ALKENE