Phase‐Transfer Catalyzed Two‐Phase Reactions in Preparative Organic Chemistry

Quaternary ammonium and phosphonium salts catalyze reactions between substances located partly in an aqueous and partly in an organic phase. Use of such phase‐transfer catalysts simplifies and accelerates numerous reactions traditionally conducted in nonaqueous media. These reactions include carbene reactions, nucleophilic substitutions, alkylations of ketones and nitriles, Wittig and Darzens reactions, formation of ethers and esters. Other reactions such as hydrolysis and oxidation can be accelerated.