Wittig reaction with ion-supported Ph3P

Ion-supported Ph₃P, 4-(diphenylphosphino)benzyltrimethylammonium bromide A and N-methyl-N-4-(diphenylphosphino)benzyl]pyrrolidinium bromide B, were used for the Wittig reaction. Ion-supported phosphonium salts A1 and B1, which were prepared from the reactions of ion-supported Ph₃P A and B with ethyl bromoacetate, respectively, reacted with aromatic and aliphatic aldehydes in the presence of K₂CO₃ to give the corresponding α,β-unsaturated ethyl esters in good yields with high purity by simple filtration of the reaction mixture and subsequent removal of the solvent from the filtrate. Similarly, ion-supported phosphonium salts A2 and B2, which were prepared from the reactions of ion-supported Ph₃P A and B with p-methylbenzyl bromide, respectively, reacted with aromatic and aliphatic aldehydes in the presence of NaH to provide the corresponding p-methylstyrene derivatives in good yields with high purity by simple filtration of the reaction mixture and the subsequent removal of the solvent from the filtrate. In both reactions, the co-product, ion-supported Ph₃PO, could be obtained quantitatively by simple filtration, and was converted into the corresponding ion-supported Ph₃P A and B again in high yields using dimethyl sulfate, followed by the reduction with LiAlH₄. Recovered and regenerated ion-supported Ph₃P A and B could be reused for the same Wittig reaction while maintaining good yields of ethyl (E)-3-(4′-chlorophenyl)-2-propenoate and 1-(4′-chlorophenyl)-2-(4″-methylphenyl)ethene with high purity by simple filtration and removal of the solvent from the filtrate.