Asymmetric Cyclization Of In-situ Formed Labile Benzoquinone Intermediates

Asymmetric catalytic reactions involving quinone compounds are receiving considerable attention due to their versatility for synthesizing chiral cyclic compounds and axially chiral biaryls skeletons.However,drawbacks such as poor stability,limited substrate scope,and poor atom-economy have limited the synthetic application of quinone compounds.In this thesis,we developed a biomimetic relay catalysis strategy that enables the oxidative conversion of readily available and stable aminophenols into labile quinone intermediates and their effective capture by a relay chiral acid catalyst for succeeding annulation.We have thus realized the first oxidative asymmetric [3+2] cyclization reaction between p-aminophenols and indoles.This protocol features high atom and step economy,high turnover of the catalyst,and excellent chemo-and stereoselectivity.The main contents of this thesis include: 1)By screening the compatibility of the catalytic oxidation system with the asymmetric induction system,we identified that the combination of salen(Mn)/TBHP and CPA enabled chemoselective oxidation of p-aminophenols and cascade enantioselective [3+2] cycloaddition reaction with indoles to prepare a series of optically pure 2,3-dihydrobenzofurodindoles in up to 91% yield and with 99% ee.The loading of catalyst could be as low as 0.01 mol% and the corresponding TON could even arrive at 4100.2)This relay catalysis strategy was further attempted for other labile quinone intermediates.The oxidative [3+2] cycloaddition reaction of p-aminophenols with styrene derivatives as well as the oxidative [4+2] coupling reaction of 2,3-dihydroxybenzoic acid and olefins have been explored,and some preliminary results have been achieved.