Synthesis and antimicrobial activity of some methyl‐2‐[ N ‐coumarin‐6′‐yl]‐3‐oxo‐2,3‐dihydro‐1 H ‐isoindolone‐5‐carboxylates

magnified image N‐substituted furylmethylimines are prepared by condensing 6‐aminocoumarins with furfural, these on sodium borohydride reduction afford N ‐[coumarin‐6′‐yl]‐2‐furylamines. Intramolecular [4+2] cycloaddition of these amines with maleic anhydride results into 3‐[ N ‐coumarin‐6′‐yl]‐4‐oxo‐10‐oxa‐3‐azatricyclo[5.2.1.0 1.5 ]dec‐8‐ene‐6‐carboxylic acids 4a , 4b , 4c . The [4+2] cycloadducts on p ‐toluene sulphonic acid treatment followed by esterification yield the titled compounds. Compound 5a , 5b , 5c was also reduced to isoindolone alcohol 7a , 7b , 7c by sodium borohydride in the presence of a base. All the compounds have been tested in vitro for their antimicrobial activity against gram‐positive bacteria Bacillus subtilis, Staphylococcus aureus , one gram‐negative bacteria, Escherichia coli , and one fungal strain Candida albicans at 100 μg/mL concentration. J. Heterocyclic Chem., 2010.