Ligand exchange reaction of sulfoxides in organic synthesis: A novel method for generation of magnesium enolates and its application to synthesis of α-halocarboxylic acid derivatives and α-haloaldehydes

Article abstract of DOI:10.1016/S0040-4020(01)90408-9

A new method for synthesis of α-halo(Cl, F)carboxylic acid derivatives and α-haloaldehydes is described. α-Halo-α-sulfinyl carboxylic acid, esters, and α-halo-α-sulfinyl aldehydes were easily prepared from aryl 1-haloalkyl sulfoxides and alkyl chloroformate and ethyl formate, respectively, in good yields. α-Chloro-α-sulfinyl amides were synthesized from (p-tolylthio)acetic acid. Ligand exchange reaction of the sulfinyl group of these acids, esters, amides, and aldehydes with ethylmagnesium bromide gave the magnesium enolates, which were treated with water to give α-halocarboxylic acid derivatives and α-chloroaldehydes in good yields. The magnesium enolates derived from the α-chloro-α-sulfinyl acid derivatives were trapped with carbonyl compounds to afford the adducts, which were transformed to α,β-epoxy carboxylic acid derivatives. Thermal elimination of the sulfinyl group in the α-halo-α-sulfinyl acid derivatives and the α-halo-sulfinyl aldehydes gave α-halo-α,β-unsaturated carboxylic acid derivatives and α-halo-α,β-unsaturated aldehydes in high yields.