Multifunctional Catalysts: Thiourea Amine Acid Salts

Significance

An efficient asymmetric vinylogous aldol reaction of 2-trimethylsiloxy furans and aldehydes catalyzed by a chiral organic salt is reported by the authors. This organic salt is generated by mixing the thiourea amine and trifluoroacetic acid in a 1:1 ratio. Under the optimized conditions (10 mol% catalyst, in chloroform or ether), the corresponding vinylogous aldol products (butenolides) can be obtained in good yields with high stereoselectivity (dr up to 96:4 and er up to 97.5:2.5). This organic salt catalyzed reaction showed a broad substrate scope: Aryl, alkenyl, and alkyl­aldehydes together with 5-substituted-2-trimethylsilyloxy furans can all be tolerated.