Synthesis of cyclic phosphonium-borate compounds through reaction of benzynes and frustrated Lewis pairs†

A practical method for the construction of stable zwitterionic phosphonium-borate compounds via trapping of benzynes by phosphine-borane frustrated Lewis pairs has been developed. A series of structurally diverse phosphonium-borate inner salts were thus prepared in moderate to good yields under mild reaction conditions. DFT calculations were also conducted to support a possible pathway of this reaction.