The Research Of Rhodium Catalyzed Synthesis Of Furans From N-Sulfonyl-1,2,3-triazoles

In recent years, N-sulfonyl-1,2,3-triazole was found to be potential diazocompound, and reactive metal carbene intermediate generated by the transition metalcatalyst is widely used in organic synthesis. The metal-catalyzed decomposition of N-sulfonyl-1,2,3-triazoles to generate transient metallocarbenes has been exploited in avariety of useful synthetic transformations, which include C-H, O-H, N-H insertion,cyclopropanation, cycloaddition and ylide formation. It can build a newcarbon-carbon bonds, carbon-hetero bond and form a cyclic compound. This papermainly focuses on the research of rhodium catalyzed synthesis of furans fromN-sulfonyl-1,2,3-triazoles.In this thesis, We used a tethered carbonyl group to trap the-imino carbeneintermediate, furan with a tosylaminomethylene group was formed after isomerization.Carbonyl triazole substrate was synthesized from ketone. By the systemicoptimization of conditions, the optimized reaction conditions is Rh2(esp)2(1mol％)in dichloroethane at reflux temperature under nitrogen atmosphere. We found thatdifferent sulfonyl group on the nitrogen atom were well-tolerated. The substituent onthe triazole has great effect on the yield, when the carbonyl group is substituted withan alkyl substituent, the yield is better; when the carbonyl group with a aryl ring wasused, the furan was obtained with moderate yield, this may due to the decreasedcarbonyl activity which has π-π conjugation with the aryl ring. When a strongelectron-withdrawing group was at the-position of the carbonyl group, thecorresponding furan was obtained in decreased yield. Using this methodology as thekey step, alkynyl furan can be easily prepared with excellent yield. Next, wehighlighted the synthetic potential of this transformation with an efficient synthesis ofphenol compound via gold-catalyzed rearrangement. Finally, We proposed a mechanism that carbonyl group attacks carbene carbon to afford furan compoundsafter isomerization.