Chen W, Fu X, Lin L, Yuan X, Luo W, Feng J, Liu X, Feng X * Sichuan University, Chengdu, P. R. of China
An Asymmetric [3+2] Cycloaddition of Alkynes with Oxiranes by Selective C–C Bond Cleavage of Epoxides: Highly Efficient Synthesis of Chiral Furan Derivatives.
Chem. Commun. 2014;
50: 11480-11483
Key words
asymmetric [3+2] cycloaddition - epoxides - furans - nickel
Significance
Tetrahydrofurans and 2,5-dihydrofurans containing a stereocenter are often found in natural products and medicinal compounds. Ni(ClO4)2·6H2O in the presence of an N,N′-dioxide ligand promotes the asymmetric [3+2] cycloaddition of alkynes with epoxides via a regioselective C–C bond cleavage to give 2,5-dihydrofurans. A catalytic amount of LiNTf2 was necessary to increase the yield of the cycloaddition process.
Comment
Notably, the asymmetric [3+2] cycloaddition of an alkene and an epoxide under optimized conditions afforded an optically active tetrahydrofuran derivative. According to the proposed activation model, the chiral nickel complex activates the epoxide to form a carbonyl ylide intermediate, through which the alkyne attacks from the re face, leading to the R-configured product.
