Highly site, regio-, and stereoselective multicomponent reaction of benzimidazole carbenes, isothiocyanates, and allenoates

The novel three-component reaction of benzimidazole carbenes with isothiocyanates and allenoates proceeded efficiently in a highly site, regio-, and stereoselective manner to produce predominantly spiro[benzimidazoline-2,3'-tetrahydrothiophene] derivatives. The reaction was proposed to occur via a tandem nucleophilic addition of carbenes to isothiocyanates followed by an unusual [3+2] cycloaddition to the less activated carbon-carbon double bond of allenoates. (C) 2007 Elsevier Ltd. All rights reserved.