1,2-Migration And Tandem Reaction Of N-aryl Pyrroles

N-aroyl pyrroles have attracted increasing attention in the field of organic synthesis due to their simple preparation and wide application.N-aroyl pyrroles served as acylating agents,they can convert into a variety of carbonyl compounds directly.Additionally,the pyrrole ring of these compounds can undergo Diels-Alder addition and conjugate addition with α,β-unsaturated aldehydes and ketones.However,most of these transformations are based on the electrical properties of the acyl group and the pyrrole ring,and there remains room for searching more interesting reactions with N-aroyl pyrroles.In this study,three synthetic methodologies were developed based on N-aroyl pyrroles and MN(SiMe3)2(M=Li,Na,K).The details were list as follow:1.1,2-Migration reaction of N-aroyl pyrroles:With N-aroyl pyrroles as starting material,2-aroylpyrroles were prepared through 1,2-migration with LiN(SiMe3)2 as base.The products of this reaction are diverse(27 examples,up to 85%yield).This new reaction for the synthesis of 2-aroylpyrroles is a complementary approach to the traditional Friedel-Crafts aroylation and VilsmeierHaack reaction.Mechanistic studies indicates that this 1,2-migration reaction is an intermolecular process.2.Aroylation reaction based on benzyl carbanion of toluene derivatives:A series of aryl benzyl ketones were synthesized by aroylation of toluene derivatives with N-aryl pyrroles in the presence of KN(SiMe3)2.In this protocol,toluene derivatives acted as both reactants and solvents.In mechanism study,we observed the initially formed product of this reaction is enolate,which couldn’t undergo further nucleophilic addition.Compared to the traditional methods,this approach does not use transition metal catalysts,and the reaction is highly versatile with yield up to 95%.3.Tandem reaction of N-aroyl pyrroles:3,4-Dihydroisoquinolin-l-ones were synthesized by tandem reaction of N-aroyl pyrroles with aromatic aldehydes.In this transfromation,NaN(SiMe3)2 not only act as deprotonation agent,it also is the nitrogen source of the final product.The novel[4+2]cycloaddition reaction presented herein is operationally-simple,straightforward,and efficient,and has good atom economical.34 diverse products were prepared with yield up to 98%.In summary,this dissertation presented three novel synthetic methods on the basis of N-aroyl pyrroles,including 1,2-migration reaction,aroylation of toluene derivatives with benzyl carboanion and tandem[4+2]-cycloaddition reaction.It provides new strategies for the synthesis of 2-aroylpyrroles,aryl benzyl ketones and 3,4dihydroisoquinolin-l-ones and may inspire new idea in the area of N-aroyl pyrrole chemistry.