Organocatalytic Synthesis of Substituted Furfuryl Alcohols and Amines

Key words

thiophene - highly substituted furans - nucleophilic activation

Significance

The authors present an organocatalytic approach for the synthesis of highly substituted furfuryl alcohols and amines in good to ­excellent yield. The reaction is catalyzed by tetrahydrothiophene (2), using a Lewis base for the ­activation of the alkynylcarbonyl derivatives 1. In contrast to 2, other Lewis bases such as DABCO or Bu₃P led to decomposition.

Comment

While electrophilic metal-catalyzed furan syntheses are common, organocatalytic approaches are rare. Inspired by the work of Krische (J. Am. Soc. Chem. 2004, 4118) and Kuroda (Tetrahedron 2004, 1913), Clark and co-workers applied a Lewis base activation concept for their reaction. By using tetrahydrothiophene (2) as a catalyst, an enolate is formed that cyclizes to a sulfur ylide containing furan which can react with different nucleophiles. This method can also be used for a multi-component domino synthesis of substituted furans.