Carbon-Carbon Bond Cleavage For Synthesis Of Biaryl Atropisomers And Spiro Compounds

Carbon-carbon bond is the basic structure in organic bond.The cleavage and reorganization of the carbon-carbon bond proves to be a powerful tool for constructing the skeleton of organic molecules,which provides a step efficient acess to complex organic molecules and natural products.In view of the good thermodynamic and kinetic stability of the carbon-carbon bond,the cleavage of carbon-carbon bond still meets great challenges.Over the past decades,organic chemists have been working to explore methods for carbon-carbon bonds activation and have made great progress.Chapter 1:This part introduces the current research progress of carbon-carbon bond activation.For strain ring molecules(mainly small ring molecules),carbon-carbon bond activation mainly depends on the release of ring strain;for non-strain ring molecules,it is necessary to introduce guiding groups to coordinate the transition metal,lowing the energy of the intermediate.Despite great progress has been made,the carbon-carbon bonds activation still meets difficulties such as method monotony and substrate limitations,and new strategies are urgent to be proposed.Chapter 2:Benefited from the torsional strain of the molecule,palladium-catalyzed enantioselective carbon-carbon bond cleavage of 9H-fluoren-9-ols was realized for biaryl atropisomers synthesis.High functional group tolerance,yields,and enantioselectivities were achieved under mild condition.The synthetic transformation of the biaryls highlighted the utility of this reaction in preparation of useful functionalized atropisomers.Chapter 3:A transition-metal free,hypervalent iodine-mediated synthesis of spiro compounds from 9H-fluoren-9-ols has been realized.The reaction may proceed via β-carbon elimination of alkoxy hypervalent iodine followed by reductive elimination of diaryl iodine and the dearomatization of the phenolic intermediate.This domino reaction efficiently constructed a special skeleton of spiro molecules in excellent regioselectivity and stereoselectivity.The above mentioned carbon-carbon bond cleavage reactions not only provided a new method for biaryl atropisomers and spiro compounds synthesis,but also showcased a new strategy for carbon-carbon bond activation:increasing the molecular torsional strain,distorting the molecule and reducing the activation energy to promoting carbon-carbon bond cleavage.