Organocatalysis of SN2 Reactions by Multifunctional Promotors: Ionic Liquids and Derivatives

摘要: We briefly review the recent experimental and theoretical developments of organocatalysis by the derivatives of ionic liquids. We focus on the efficiency of rate enhancement and mechanistic features of SN2 reactions exhibited by ionic liquid derivatives. Roles of various moieties in the ionic liquid—oligoethylene glycol complexes, specifically, their synergistic collaboration for organocatalysis, are described in detail. Two alternative mechanisms are presented for SN2 reactions promoted by ionic liquid derivatives. When [mim- t OH][OMs], in which the ionic liquid [mim][OMs] and t-butyl alcohol are fused by covalent bonding, is used as a promotor, the metal salt MX reacts as a contact ion-pair (CIP). The oxygen atoms in the promotor bind to the counterion M+ to alleviate its Coulombic influence on the nucleophile X−, enhancing the nucleophilicity. For SN2 reactions promoted by [hexaEGim …