Asymmetric Synthesis of Hydrodibenzofurans from Norcaradienes: Kinetic Resolution via [3 + 2] Cycloaddition with Quinones

Abstract

The catalytic asymmetric [3 + 2] cycloaddition of racemic norcaradienes with quinones to construct multicyclic hydrodibenzofurans was achieved by the use of chiral N,N′dioxide/metal complex catalysts. Kinetic resolution of norcaradienes accompanied by partial racemization occurred, and one enantiomer in prior acted as the C 2 synthon to participate in diastereoselective cycloaddition. An enantiodivergent synthesis via a switch of metal ions was observed when naphthoquinone was used as the partner. DFT calculations revealed the profiles of the cycloaddition processes.

Enantioselective Synthesis of Spiro[cyclopentane-1,3′-oxindole] Scaffolds with Five Consecutive Stereocenters

“…Benefiting from their stable configurations and adjustable chiral pocket, chiral N , N ′-dioxide–metal complexes have been successfully applied in a number of cycloaddition reactions and other asymmetric transformations . Inspired by Yan’s work (Scheme c) and as part of our ongoing interests on the concise synthesis of enantioenriched chiral spiro-oxindole molecules, we envisioned that a chiral N , N ′-dioxide–metal complex Lewis acid catalyst was a potential promoter for the cascade reaction cascade annulation reaction of MBH maleimides of isatins with ortho -hydroxychalcones.…”