ALTERNATE SYNTHESIS ROUTE OF 2-(SUBSTITUTED PHENYL)-3,3a-DIHYDRO-8H-PYRAZOLO[5,1-a]ISOINDOL-8-ONES VIA CHALCONE-BASED N-FORMYL-PYRAZOLINES

作者：Ahmed Naseem^*; Dev Dharm

来源：Synthetic Communications, 2013, 43(5): 689-704.

DOI：10.1080/00397911.2011.606414

• Chalcone N-formyl-2-pyrazoline
• Friedel-Crafts acylation
• 2-(substituted phenyl)-3,3a-dihydro-8H-pyrazolo[5,1-a]isoindol-8-ones

An alternate approach to 2-(substituted phenyl)-3,3a-dihydro-8H-pyrazolo[5,1-a]isoindol-8-ones via chalcone-based N-formyl-pyrazolines is described. N-Formyl-pyrazolines were prepared in excellent yield (81-96%) by the reaction of chalcones with hydrazine hydrate in the presence of formic acid, which undergoes intramolecular Friedel-Crafts acylation in the presence of trifluoroacetic acid (TFA) as a catalyst to afford functionalized 2-(substituted phenyl)-3,3a-dihydro-8H-pyrazolo[5,1-a]isoindol-8-ones in good to excellent yield (74-94%) at reflux in acetonitrile. Our synthetic route avoids expensive reagents and significantly improves yields.

• 出版日期2013