New N-bridgehead heterocyclic compounds. I. Carbamoyl-substituted indolizines and benzoindolizines

Synthesis and spectroscopic properties of novel indolizines and azaindolizines

“…[27][28][29][30] Usually, this multistep process starts with the preparation of N-heterocyclic quaternary salts with -halo carbonyl compounds, in situ conversion into corresponding heterocyclic N-ylides in the presence of an inorganic or organic base and 3+2 dipolar cycloaddition reactions of heterocyclic N-ylides with electron-deficient alkynes or alkenes. [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] Our group has developed a simple one-pot, multicomponent synthetic strategy towards N-bridgehead heterocyclic compounds based on the consecutive quaternization of the N-heteroaromatic compound, in situ generation of the heterocyclic N-ylide, 3+2 dipolar cycloaddition reaction to an electron-deficient alkyne and aromatization sequence, using an epoxide as solvent and acid scavenger. [46][47][48][49][50][51][52][53][54][55] A range of new indolizines and azaindolizines were synthesized via 3+2 dipolar cycloaddition reactions of cycloimmonium ylides, generated from the various N-heterocycles such as pyridine, quinoline, isoquinoline, pyridazine, pyrimidine, phthalazine and benzimidazole derivatives with diverse phenacyl bromides, alkyl bromoacetates, 3-(2-bromoacetyl)-2H-chromen-2-one and electrondeficient alkynes.…”