A trifluoroacetic acid-mediated cascade reaction involving nucleophilic substitution and Smiles rearrangement is described. The reaction of hydroxydihydrodiazepines with primary amines led to amino-substituted dihydrodiazepines, which readily underwent Smiles rearrangement to give pyrrolo[1,2-f]pteridine derivatives.

Simple aromatic substituents in the substrate molecule, including pyrimidine, pyridine, and benzene rings, directly facilitated the intramolecular cycloaddition of azomethine ylide to alkene. All of these aromatic substituents aided the formation of azomethine ylides, which then underwent highly diastereospecific sequential cycloaddition. It was shown that both the presence of an electron-deficient aromatic ring and a substituent at ortho position of the aromatic ring relative to the aminomethyl group enhanced the reactivity of azomethine ylides towards cycloaddition.

An efficient and practical method has been developed for the synthesis of 6-aryl-substituted pyrido[2,3-b][1,4]benzoxazepines via a Friedel−Crafts reaction of readily accessible 2-phenoxypyridin-3-amines and aromatic acids.

A one-pot three-component reaction, involving condensation of 2-aminopyridines, aldehydes, and ketones/aldehydes under trifluoromethanesulfonic acid catalysis, provides rapid access to highly substituted novel 4H-pyrido[1,2-a]pyrimidines.Keywords: 2-aminopyridine; 4H-pyrido[1,2-a]pyrimidine; MCRs; multicomponent reactions; three-component reaction