BF3•OEt2-Catalyzed Unusual Formation of cis-2,3-Disubstituted Tetrahydrofuran Scaffolds

Aldehydes undergo smooth cyclization with 4-(phenylthio)but-3-en-1-ol in the presence of BF3 center dot OEt2 in dichloromethane at room temperature to afford a novel class of 2,3-disubstitued tetrahydrofurans in good yields with all-cis-selectivity. This method is simple, selective, and convenient for the synthesis of tetrahydrofuran scaffolds in a single step.