A select route: By selecting the appropriate ligand, dihydrofurans and dihydrobenzoxepines can be chemoselectively formed in moderate to good yields with good to excellent diastereocontrol from identical starting materials (see scheme).
Highly Enantioselective Synthesis of Multifunctionalized Dihydrofurans by Copper-Catalyzed Asymmetric [4 + 1] Cycloadditions of α-Benzylidene-β-ketoester with Diazo Compound
Highly efficient synthesis of chiral tetrasubstituted 2,3-dihydrofuran derivatives has been realized by Cu-catalyzed asymmetric [4 + 1] cycloadditions of alpha-benzylidene-beta-ketoester with a diazo compound. Following this methodology, a series of optically active multifunctionalized dihydrofurans were prepared in high yield with up to 96% ee and 99/1 dr.