Synthesis of Quinolizinium and Pyridinium Salts

Similarly, we have developed a new Rh(III)-catalyzed, azo-assisted C-H activa-tion/annulation reaction of azobenzenes with alkynes to give multisubstituted cinnolinium salts 112 in good to excellent yields [54]. The reaction is compatible with various functional groups and proceeds under mild reaction conditions using air as the cooxidant. These cinnolinium salts have been further modified into three different iV-heterocycles indoles, rndoloindoles, and cinnolines (Eq. (5.106)). 

Recently, Glorias discovered a Rh(III)-catalyzed coupling of oximes with electron-deficient diazo compounds to give iV-oxides of isoquinoline and pyridine [55]. The reaction proceeds with the liberation of H2O and Nj as by-products. In this reaction, the insertion of Rh-carbene into ortho-C-H bond followed by intramolecular dehydrative annulation plausibly accounts for the generation of Af-oxides (Eqs. (5.107) and (5.108)). The diazo compounds functioned as equivalents of electron-deficient alkynes, enriching the product diversity of isoquinoline and pyridine synthesis. 

---