Base-Mediated Cascade Aldol Addition and Fragmentation Reactions of Dihydroxyfumaric Acid and Aromatic Aldehydes: Controlling Chemodivergence via Choice of Base, Solvent, and Substituents

Article abstract of DOI:10.1021/acs.joc.8b01867

The diester derivative of dihydroxyfumaric acid (DHF) has been used exclusively as an electrophile in organic synthesis. However, the synthetic utility of DHF's nucleophilic reactivity, contained in the ene-diol moiety, has been underexplored. Inspired by recently observed pH-dependent chemodivergent nucleophilic aldol reactions of dihydroxyfumarate (DHF^2-) with glyoxylate and formaldehyde, we report herein the control and synthetic application of base-controlled chemodivergent reactions between dihydroxyfumarate and aromatic and heteroaromatic aldehydes. With hydroxide as the base in a predominantly aqueous medium, aldol addition followed by deoxalation occurs to provide various 3-aryl-2,3-dihydroxypropanoic acids. With triethylamine as the base in THF, 1-aryl-2,3-dihydroxypropanones are the products of the reaction. In order to understand the difference in reactivity between DHF, its dicarboxylate, and its dimethyl ester, we undertook computational and experimental studies that provide a rationale as to why the dihydroxyfumarate (DHF^2-) is a nucleophile while the corresponding diester reacts as an electrophile.