Regioselective Annulation of 3(5)‐Aminopyrazole with Aryl Ketones or Aryl Alkynes Using N,N‐Dimethylethanolamine as a Single/Triple Carbon Synthon

An efficient and regioselective cyclization for construction of pyrazolo[3,4‐ b ]pyridines and methylene‐bridged bis(pyrazolo[1,5‐ a ]pyrimidines) has been established. It involves a [3+2+1] annulation of 3(5)‐aminopyrazole, N,N ‐dimethylethanolamine (DMEA), with 1,2‐insertion of aryl methyl ketones or 2,1‐insertion of aryl alkynes. DMEA is oxidized through C( sp 3 )‐H activation to provide a single or triple carbon source.