The Synthesis And Performance Of Carbohelicenes

Helicene is a kind of fascinating molecules with chiral helix structure,Because of its special helical structure,the helicenes have a high degree of conjugation,and they exhibit a strong optical rotation,making the helicenes in chemical sensing,supramolecular materials,molecular recognition,and chiral catalysis attract much attention.At present,the synthetic methods of helicene include photocyclization,Friedel-Crafts-Type reactions,Diels-Alder reactions and Metal-Catalyzed Cyclizations.However,the photocyclization is still the main way of synthesis.The general synthetic helicenes are racemates,and the analysis and separation of chirality is particularly important.Chiral helicenes are synthesized by the separation of racemate,asymmetric synthesis and chiral source induction.Binaphthol is a typical C2-axis chiral compound.Because of its special properties,it has become a hot spot in the world,especially in stereochemistry.In this paper,the chiral chirality is induced by the axial chirality of binaphthol.Therefore,we used binaphthol as a precursor and synthesized a helicene precursor,alkenes,through a series of simple and convenient methods,then,the alkenes are then ring-cycled to form helicenes.In addition to the low concentration of the solution in the light reaction,the other reactions are simple and classic,with high yield and security.The structure of synthesized chiral helicenes was determined by NMR,MS,and single crystal.The spectral properties of UV,fluorescence,and polarimetry were studied.The axial chirality of binaphthol can induce the synthesis of specific chiral helicenes: R-binaphthol induces the formation of(R,M),(R,P)chiral helicenes,with a ratio of 1:2.4.S-binaphtol induces(S,P),(S,M)helicenes,their ratio is 1:2.4.The diastereoselectivity for [6]helicene is a general level with a de value of 41%.However,it was unexpected that during the experiment we found that two different chiral hexospines can be separated by simple column chromatography without the need ofexpensive liquid chromatography and chiral reagents to split and pass.The chirality of the chiral helicenes separated by column chromatography was greater than 98%.For[7]helicene,R-Binaphthol induces the formation of(R,R,P)and(R,R,M)configuration,while S-Binaphthol induces the formation(S,S,M)and(S,S,P)configuration.The ratio of the two diastereomers was 1:2.5,the de value was 43% and the inductive capacity was moderate.Similar to [6]helicene,they can be separated by simple column chromatography to give chiral spirones with an ee greater than99%.Finally,a series of multi-oxa helicene were obtained by oxidation of naphthol hydroxyl terminated at the end of spironene.It was found that the chirality of [6]helicene can affect the chirality of oxa [5]helicene,(P)-helicene to(M)-oxa[5]helicene,(M)-helicene to(P)-oxa [5]helicene,Their optical properties were tested.