Study On Organic Reactions Catalyzed By Copper N-heterocyclic Carbene

Organometallic chemistry is a multidisciplinary field of chemistry.Its application in catalytic reaction promoted the development of chemical industry,and it provides many highly efficient and selective methods for organic synthesis.N-heterocyclic carbenes(NHCs)is realized as ancillary ligands in organometallic catalysis.In conjunction with copper,the strong electronic donating properties of NHCs gives yield to catalysts that are often very robust,demonstrating air,moisture and thermal stability.In the last decade,NHC ligated copper complexes act as catalysts for functionalization carbonyls,alkenes and alkynes.Herein,the Cu-NHC complexes act as catalysts for four types of organic catalytic reactions.(1)Cu-NHC complexes could be readily used as catalyst for aerobic oxidation of alcohols to aldehydes at room temperature.It seemed that this method was not only suitable for benzylic alcohol;heterocyclic substrates could also be afforded in excellent yields.Besides,we have extended our alcohol substrates to cinnamyl alcohol and aromatic ketone was afforded in 95%yield.The method provides a new route for the synthesis of aldehydes and ketones which might need noble metal catalyst or TEMPO as the previous literature reported.(2)Cu-NHC complexes could be also used as catalyst for reduction of imines to amines at room temperature,and based on the aerobic oxidation of alcohols to aldehydes,we also explored one-pot tandem synthetic strategy,providing greener and practical approaches for preparation of secondary amines from alcohols and amines.(3)Cu-NHC complexes could be competent for the synthesis of formaldehyde dialkyl acetals from alcohols or phenol with dichloromethane in base.It was also an efficient catalyst for the preparation of unsymmetrical ether from the etherification of p-toluyl alcohol and n-Butyl chloride.Compared with early literature,which needed high temperature for a long time to synthesize the formaldehyde dialkyl acetals,or used dibromomethane as a source of methylene,the transformation proceeded in high yields at room temperature for 2 hours.(4)Aryl fluorosulfates could be simply synthesized from phenols and SO2F2 in high yields,which can be used as alternatives to halides or triflates,and were employed as coupling partners with propiolic acid in the Sonogashira reaction.(PPh3)4 and Cu-NHC complexes act as catalysts for the synthesis of symmetrical diarylalkynes via the coupling reaction of aryl fluorosulfates and propiolic acid.We could also get the unsymmetrical diarylalkynes via the coupling reaction of aryl fluorosulfates,iodobenzeneand propiolic acid in good yields.The method is also potentially useful for the synthesis of some biologically active moleculesthe such as Combretastatin A4.The other part of the paper described synthesis of diaryl sulfates at room temperature for 1 hour which has found considerable utilitities as alkylating agents.