Solid-phase synthesis of N-(buta-2,3-dien-1-yl)amides by the Crabbé reaction

The Crabbé homologation of polymer-supported propargylamine with paraformaldehyde, CuI, and dicyclohexylamine in 1,4-dioxane at 100 °C, followed by cleavage with dilute trifluoroacetic acid, furnishes N-(buta-2,3-dien-1-yl)amides as isolable products. The N-acyltriazene linker on Merrifield resin serves simultaneously as a protecting group for the nucleophilic primary amine. The product diversity is achieved by altering the acyl chloride in the acylation of the triazene linker. In addition to being a new route to nitrogen-containing allenes, our solid-phase method enables immobilization of these reactive cumulated dienes for further synthetic operations.