Indolizines and pyrrolo[2,1-a]isoquinolines are synthesized by 1,3-dipolar cycloadditions of pyridinium benzotriazolylmethylides or isoquinolinium benzotriazolylmethylides with ethylenes and acetylenes.

The syntheses of chiral 2-substituted and 2,6-disubstituted piperidines, and piperidin-2-ylphosphonates, via benzotriazole methodology are described.

2-Aminopyridines 1a-c and 1-aminoisoquinoline with 1-chloromethylbenzotriazole give 2-amino-1-[alpha-benzotriazol-1-ylmethyl]pyridinium chlorides 2a-c and 1-amino-2-(alpha-benzotriazol-1-ylmethyl)isoquinolinium++ + chloride 12, respectively. Compounds 2a-c and 12 react with aryl aldehydes 3a-h to afford imidazolo[1,2-a]pyridines 7a-k and imidazolo[2, 1-a]isoquinolines 13a,b in good yields.