A highly efficient microwave-assisted copper(II)-catalyzed cyclization cascade was established starting from readily accessible O/N-propargylated 2-hydroxy or 2-aminobenzaldehydes and o-phenylenediamines to synthesize densely functionalized imidazo [1,2-d][1,4]oxazepines and imidazo [1,2-d][1,4]diazepines in high yields (up to 93%). This one-pot two-step process was found to be highly atom economical (−H 2 O, −H 2 ) and operationally simple and enabled the generation of two new heterocycle rings (seven-and five-membered) and three new C−N bonds in a single synthetic operation. These reactions well tolerated a variety of substituents including electron-donating and electron-withdrawing groups and furnished the desired fused heterocycles in high yields under microwave irradiation in a very short reaction time. The mechanism of the established protocol involves sequential imine formation−intramolecular cyclization−air oxidation followed by 7-exo-dig cyclization steps. A comparative study between the microwave-assisted approach and conventional heating was also performed to demonstrate the advantages of the microwave-assisted protocol in terms of high yield and shorter reaction time.

A microwave-assisted, copper-catalyzed, one-pot, two-step reaction was established to access functionalized [1,6]-naphthyridines in high yields (up to 96%) starting from 2-(N-propargylamino)benzaldehydes and arylamines. This rapid and operationally simple sequential reaction...

A solvent-dependent chemodivergent approach was developed for the synthesis of 6,12-methanodibenzo[b,f][1,5]diazocin-13-ylmethanones and 2,3,4-trisubstituted 1,2,3,4-tetrahydroquinolines involving two distinct AB2 and A2B2 multicomponent processes.

An efficient, diversity-oriented synthesis of oxazepino­[5,4-b]­quinazolin-9-ones, 6H-chromeno­[4,3-b]­quinolines, and dibenzo­[b,h]­[1,6]­naphthyridines was established involving a substrate-based approach under microwave-assisted and conventional heating conditions in high yields (up to 88%). The CuBr2-catalyzed, chemoselective cascade annulation of O-propargylated 2-hydroxybenzaldehydes and 2-aminobenzamides delivered oxazepino­[5,4-b]­quinazolin-9-ones involving a 6-exo-trig cyclization-air oxidation-1,3-proton shift-7-exo-dig cyclization sequence. This one-pot process showed excellent atom economy (−H2O) and constructed two new heterocyclic rings (six- and seven-membered) and three new C–N bonds in a single synthetic operation. On the other side of diversification, the reaction between O/N-propargylated 2-hydroxy/aminobenzaldehydes and 2-aminobenzyl alcohols delivered 6H-chromeno­[4,3-b]­quinolines and dibenzo­[b,h]­[1,6]­naphthyridines involving sequential imine formation-[4 + 2] hetero-Diels–Alder reaction-aromatization steps. The influence of microwave assistance was superior to conventional heating, where the reactions were clean, rapid, and completed in 15 min, and the conventional heating required a longer reaction time at a relatively elevated temperature.