American Chemical Society
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Brønsted Acidity of Substrates Influences the Outcome of Passerini Three-Component Reactions

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journal contribution
posted on 2009-07-17, 00:00 authored by Babajide O. Okandeji, Jason K. Sello
Passerini three-component reactions of aldehydes, isocyanides, and strong carboxylic acids (i.e., pKa < 2) yield α-acyloxycarboxamides and/or α-acylaminocarboxamides, the characteristic products of Ugi four-component reactions. We propose that α-acylaminocarboxamide formation with these substrates is a consequence of in situ Brønsted acid-catalyzed reaction of the isocyanide and aldehyde to yield an imine that participates in an Ugi-type reaction. The apparent transfer of the isocyanide α-carbon to protic solvents as a formyl group during imine formation is indicative of new isocyanide reactivity.