Rh(I)-catalyzed three-component reaction of 2,3-allenoates, organoboronic acids, and aldehydes. An efficient synthesis of α,β-unsaturated δ-lactones

α,β-Unsaturated δ-lactones were efficiently prepared by an Rh(I)-catalyzed three-component reaction of 2,3-allenoates, organoboronic acids, and aldehydes. The reaction may proceed via a sequential transmetalation, carbometalation of 2,3-allenoates, insertion of aldehydes, and lactonization process.