Polyhaloalkanes as the C1 source: radical-mediated migratory carbonylation of alkenes with polyhaloalkanes toward α,β-unsaturated carbonyls

Abstract

An unprecedented copper-promoted radical-mediated alkenyl C(sp²)–H carbonylation of alkenes with polyhaloalkanes for divergently producing α,β-unsaturated esters and aldehydes is presented. Employing polyhaloalkanes as the carbonyl C1 sources enables the carbonylation of the alkenyl C(sp²)–H bonds via a polyhaloalkyl radical addition, alkene alkoxypolyhaloalkylation and carbonylation cascade and provides general, stereoselective, and chemodivergent access to α,β-unsaturated esters and aldehydes relying on the nucleophile choice. Experimental mechanistic studies and DFT calculations indicate that transformation of polyhaloalkanes into polyhaloalkyl C(sp³)-centered radicals by single electron transfer of the in situ aryl radicals from aryl diazonium salts is crucial, and this process represents a new radical-mediated pathway featuring polyhaloalkyl radical addition across alkenes to generate the key 1-alkoxyl-2-polyhaloalkyl alkane intermediate followed by thermodynamic alkoxy-migratory carbonylation.