Synthesis Of Chiral ?-pyrones And Esters Under The Catalysis Of Nitrogen Heterocyclic Carbene

Nitrogen heterocyclic carbenes(NHCs)with unique electronic properties are widely used in asymmetric catalytic reactions.The extensive demand for chiral structure control of organic compounds also increases the development of efficient asymmetric catalytic reaction systems by NHCs catalyzed.In this study,the synthesis of chiral ?-Pyranone from aldehydes and 2-aryl ketones under the action of Nitrogen Heterocyclic Carbene [3+3] cycloaddition reaction and the synthesis of benzyl benzoate derivatives by multi-component one-pot esterification catalyzed by Nitrogen Heterocyclic Carbene were introduced respectively.Firstly,the chiral ?-Pyranone and its derivatives were synthesized by the [3+3]cycloaddition reaction of ?,?-unsaturated aldehyde and 2-aryl ketone under the catalysis of Nitrogen Heterocyclic Carbene.Through the screening of catalyst,solvent,alkali and temperature,the optimum reaction conditions were determined as follows:toluene as solvent,DBU as alkali,and reaction temperature 0 ?.Based on these conditions,the generality of the reaction was explored,sixteen novel ?-Pyranone derivatives were obtained with high yield(up to 98%)and high enantioselectivity(up to 99% ee).The structures of the compounds were characterized by NMR and MS,and the reaction mechanism was also studied.The method is easy to operate and has good regional selective control,which makes it have great application prospect in medicine.Secondly,the synthesis of benzyl benzoate analogs by one-pot esterification of benzyl bromide and p-nitrobenzaldehyde under the catalysis of Nitrogen Heterocyclic Carbene was introduced.Through investigating the influence of catalyst,solvent,alkali,temperature,time and other factors on esterification reaction,the optimal conditions were determined to use nitrogen heterocyclic carbene as catalyst,THF as solvent,DIPEA as alkali,reaction at 50 ? for 36 h,the yield can reach 97%.On this basis,we explored its universality,synthesized nine derivatives,confirmed their structures by NMR and MS,and finally explored the reaction mechanism.