Chemical transformations of quaternary ammonium salts via C-N bond cleavage

Quaternary ammonium salts are readily prepared and show good reactivity in various organic transformations via C-N bond cleavage. In this review we summarize reactions of aryl, benzyl, allyl and propargyl quaternary ammonium salts including cross-coupling with organometallic reagents, as arylation or benzylation reagents in C-H functionalization, reductive deamination, reductive coupling, nucleophilic substitution, carboxylation with CO2, and carbonylation with CO to construct C-C, C-H and C-heteroatom bonds.