Proline-Mediated Baylis–Hillman Reaction of Methyl Vinyl Ketone without a Co-catalyst under Solvent-Free Conditions

Abstract

A proline-mediated Baylis–Hillman reaction of methyl vinyl ketone with aromatic aldehydes has been carried out without using any co-catalyst, under solvent-free conditions. The reaction works efficiently at 60 °C in the presence of a small amount of water to afford the Baylis–Hillman adducts in reasonable to very good yields over 8–48 h. The absence of a co-catalyst suggests that proline plays a role in the proton-transfer step of the reaction mechanism, in addition to its proposed involvement in the iminium ion formation and conjugate addition. This would, in principle, imply that proline acts as a trifunctional catalyst in the reaction, and mechanistic studies to gain a deeper understanding of this aspect should provide further insights in the future.

Key words

Baylis–Hillman - proline - methyl vinyl ketone - solvent-free - co-catalyst - organocatalysis

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