An efficient and practical A(3)-coupling based reaction that gives a variety of 2,5-polysubstituted dihydrofurans and 2,5-disubstituted furan derivatives has been developed. This domino copper-catalyzed three-component coupling reaction of propargylic alcohol, ethyl glyoxalate, and an amine affords a propargylic amine intermediate, which undergoes an alkyne-allene isomerization followed by a cyclization to yield the dihydrofuran. Upon treatment with CH3I and base, the latter was smoothly converted into a 2,5-disubstituted furan. Alternatively, the furan derivatives can be directly prepared by a two-step reaction sequence.
Fan W,Ma SM. Copper(I)-Catalyzed A(3)-Coupling Based Reaction of Alkynes, Aldehydes, and Amines: An Efficient Approach to 2,5-Polysubstituted Dihydrofurans and 2,5-Disubstituted Furans[J]. Eur. J. Org. Chem.,2015(16):3531-3539.