Synthetic and mechanistic aspects of the reactions between bromodifluoromethyltriphenylphosphonium bromide and dibromofluoromethyltriphenylphosphonium bromide and trialkylphosphites
作者:Richard M. Flynn、Donald J. Burton、Denise M. Wiemers
DOI:10.1016/j.jfluchem.2008.04.003
日期:2008.7
exchange process involves the formation of difluorocarbene via dissociation of the intermediate difluoromethylene ylide, capture of the difluorocarbene by the trialkylphosphite to give [(RO)3P+CF2−], which captures bromine followed by dealkylation to the product, bromodifluoromethylphosphonate. The equilibria involved in the multi-step mechanism are all shifted to the phosphonate product by the final dealkylation
The synthesis of α-fluoroacrylates and α-bromo-α-fluoroalkenes was achieved in very good yields using aldehydes and ketones, triphenylphosphine, diethylzinc as promoter, and ethyl dibromofluoroacetate or dibromofluoromethane, respectively. A change in the addition sequence was critical in order to obtain exclusively α-fluoroacrylates in good yields.