Iron-Facilitated Oxidative Radical Decarboxylative Cross-Coupling between α‑Oxocarboxylic Acids and Acrylic Acids: An Approach to α,β-Unsaturated Carbonyls
The
first Fe-facilitated decarboxylative cross-coupling reaction
between α-oxocarboxylic acids and acrylic acids in aqueous solution
has been developed. This transformation is characterized by its wide
substrate scope and good functional group compatibility utilizing
inexpensive and easily accessible reagents, thus providing an efficient
and expeditious approach to an important class of α,β-unsaturated
carbonyls frequently found in bioactive compounds. The synthetic potential
of the coupled products is also demonstrated in subsequent functionalization
reactions. Preliminary mechanism studies suggest that a free radical
pathway is involved in this process: the generation of an acyl radical
from α-oxocarboxylic acid via the excision of carbon dioxide
followed by the addition of an acyl radical to the α-position
of the double bond in acrylic acid then delivers the α,β-unsaturated
carbonyl adduct through the extrusion of another carbon dioxide