Novel reactions of beta-oxidophosphonium ylides with perhaloalkanes - A facile route to trisubstituted halo olefins

beta -Oxidophosphonium ylides as nucleophiles react readily with various pe rhaloalkanes via halophilic attack on C-X(X=I, Br or Cl)bonds to form alpha -halosubstituted betaine intermediates, which can be transformed to situ i nto Z- isomers of chloro-, bromo- or iodo-substituted olefins as major prod ucts in good yields. These novel reactions may afford a facile route to var ious trisubstituted halo olefins by means of beta -oxidophosphonium ylides prepared in situ from various phosphonium salts and aldehydes.