Visible Light-induced Decarboxylation Of Heterocyclic Nitrogen Oxides With Phthalimide Esters

Nitrogen containing heterocyclic compounds which have unique structures and potential medicinal value are widely persentin drug molecules and natural compounds.Therefore,the method of introducing functional groups into these compounds has been widely concerned by chemists in recent years.The most common and direct method is to completethe coupling of C-C bond and C-X(X=N,O,P,S,etc.)bond by activating C-H bond.In this paper,we studied the visible light induced alkylation of heterocyclic nitrogen oxides without the presence of transition metals.The reaction conditions are mild,environmentally friendly and easy to operate.This method provides a new synthetic strategy for the synthesis of ortho-substituted quinoline and pyridine compounds.The main research contents of this paper include the following parts:The first part:Based on the investigation of the literatures related to nitrogen-containing heterocyclic compounds and phthalimine(NHPI)esters,the experimental ideas were proposed and the experimental programs were designed.First,more than a dozen nitrogen-containing heterocyclic nitrogen oxides were synthesized,including methyl,halogen,cyano and other substituent groups with different electronic effects.Next,more than ten kinds of NHPI esters containing primary,secondary and tertiary carboxylic acid derivatives were synthesized.The second part:Under the induction of visible light,study the alkylation reaction of quinoline nitrogen oxide and pyridine nitrogen oxide C(sp~2)-H bond activation.The reaction conditions such as photocatalyst,solvent,and alkali were screened.Finally,the optimal reaction condition were determined.The third part:With the optimal reaction condition in hand,we explored the scope of heterocyclic nitrogen oxides and NHPI esters.More than 30 different products were successfully synthesized,the best yield could up to 98%.The above results showed high functional group tolerance and very good substrate scope.The free radical capture and clock experiment confirmed that free radical was likely involved in this reaction which induced by visible light.The preliminary study on the mechanism showed that the ground state photocatalyst was excited under visible photo irradiation reacts with NHPI ether via SET to generate the alkyl radical which reacted with heterocyclic nitrogen oxides to realize the ortho alkylation of heterocyclic nitrogen oxides.