Studies On Structure,racemization And Arylation Of [5]Helicene

In this paper,the research progress of aromatic compounds,including benzene,naphthalene,phenanthrene and phenanthrene structure,was reviewed.By understanding the structural properties and preparation of aromatic compounds,the reactions involved in aromatic compounds,and researching on the application of aromatic compounds in practical production and our life,leads to study on the synthesis of[5]helicene and some properties such as palladium catalyzed C-H aromatization and photocyclization to obtain[5]helicene derivatives,methylated,dibromided and debrominated closure ring reaction of 2,2'-bis(trifluoromesylate)-1,1'-binaphthalene to synthesis[5]helicene derivatives and the bromination derivatives of[5]helicene are obtained by debroming and ring closing of t-Bu OK.Understanding of the racemization,stability exploration,asymmetric synthesis application,optical,thermal and electrochemical properties of[5]helicene,leads to study on the structure,racemization and arylation of[5]helicene..The racemization rate and time curve of[5]helicene is measured by HPLC in chloroform and tetrahydrofuran,confirming that the relationship between the value of ee and time varying is a linear.The Gibbs activation energy 24.35 kcal/mol and 24.46kcal/mol is obtained in chloroform and tetrahydrofuran by combining Eyring equation and logarithmic racemization rate curve.In view of the structure of[5]helicene,a two-dimensional hydrogen spectrum identification was obtained to complete the attribution of the hydrogen of[5]helicene.The structure of the[5]helicene was confirmed by X-ray single crystal diffraction.As for the synthesis derivation of[5]helicene,including the coupling structure of?-chlorine,?-bromine,?-methoxy,?-methyl,?-amyl,?-acetyl,3-hydroxyl substitution of benzene,biphenyl and the coupling structure of thiophene,pyridine and furan heterocyclic rings,providing a palladium catalyzed method to prepare[5]helicene derivative by Suzuki coupling reaction with using 7,8-dibromo[5]helicene and arylboronic acid or heterocyclic boric acid,the yield is up to 62%.Their structures are determined by ¹H-NMR and ¹³C-NMR.UV-vis and fluorescence spectra are measured for the[5]helicene derivatives,the maximum absorption wavelength changes a little comparing to[5]helicene.However,it can be confirmed that the phenomenon of red-shift occurred to different degrees,7,8-di(biphenyl)[5]helicene owing the biggest maximum absorption wavelength(405nm)among them.Similarly,in the fluorescence spectrum analysis,also leads to a red-shift to different degrees,in which the maximum emission wavelength of the 7,8-difuran[5]helicene is 454 nm,which is the largest value in the measured maximum emission wavelength,increasing a 24 nm comparing with[5]helicene.