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Asymmetric Synthesis of Furo[3,4-b]indoles by Catalytic [3+2] Cycloaddition of Indoles with Epoxides.

A highly efficient N,N'-dioxide-Ni(II) catalyst system for the catalytic [3+2] cycloaddition of indoles with epoxides through C-C cleavage of oxiranes was accomplished under mild conditions. It provided a promising approach for chiral furo[3,4-b]indoles in up to 98% yield with up to 91% enantiomeric excess (ee) and >95:5 diastereomeric ratio (d.r.).