Study On Ring-Opening Reaction Based On Torsional Strain Of Fused Biaryl Compounds

Multiple substituted biaryl compounds exhibit optical activity due to the inhibited rotation along the aryl-aryl single bond,and their unique properties have attracted significant attention.On the other hand,ring-strain plays an important role in the ring-opening reaction of cyclic compounds.In this thesis,we studied torsional strain of biaryl cyclic compounds,which was raised by the distortion of the molecule.The ring-opening reaction of these distorted molecule have been investigated.This thesis is divided into the following four chapters:The first chapter:Small ring compounds and their synthetic applications.This chapter provides a summary of strain enery and ring-opening reactions of three-and four-membered cyclic compounds.The ring-strain activates the σ bond on these small rings,thus promotes the ring-opening or ring-expansion reactions.The second chapter:The synthesis of bridged biaryl axially chiral compounds via sequential Cu-catalyzed ring-opening and Pd-catalyzed Heck cyclization.We have developed a copper/(chiral oxazoline)catalyzed asymmetric ring-opening reaction of five-membered diaryliodonium salts by using carboxylic acids as the coupling partner.The obtained highly optically active atropisomers can undergo Pd/Cu co-catalyzed Heck cyclization to give seven-membered lactones bearing chiral axis and stereogenic carbocenter.The third chapter:Oxone-mediated oxidative ring-opening of 9H-fluorenol.A method for the synthesis of 2-hydroxybiaryl compounds from 9H-fluorenol was developed in the presence of Oxone in hexafluoroisopropanol and water(20:1).9H-Fluorenol generates triaryl carbocation under acidic conditions,which undergoes Baeyer-Villiger type oxidative rearrangement to deliver the target product.The forth chapter:Theoretical calculation of torsional strain of cyclic biaryl compounds.We obtained the ring strain energies of the six classes of cyclic compounds by calculation.The difference between the hydrogenation energies of 4,5-substituted compounds and 4,5-hydrogen-substituted compounds is regarded as the torsional strain energy.It was found that the larger the twist angle,the greater the torsional strain of the compound.