Facile, Stepwise and Diversity Oriented Synthesis of 3-(2-Oxo-2H-Chromen-3-yl)-1-Phenyl-1H-Pyrazole-4-Carbaldehydes

Devulapally Srikrishna and Pra

Abstract

3-Acetyl-2H-chromen-2-ones (1) when treated with phenylhydrazine in acetic acid gave 3-(1-(2-phenylhydrazono)ethyl)-2H-chromen-2-one (2) which on Vilsmeier-Haack formylation yielded the title compound, 3-(2-oxo-2H-chromen-3-yl)-1-phenyl-1H-pyrazole-4-carbaldehyde (3). Alternatively, 3 could also be prepared in a stepwise manner by treating 1 with DMF-DMA to yield 3-(3-(dimethylamino)acryloyl)-2H-chromen-2-one (4) followed by reaction with phenylhydrazine leading to 3-(1-phenyl-1H-pyrazol-3-yl)-2H-chromen-2-one 5 and its subsequent treatment with the Vilsmeier-Haack reagent. Also, 3 could be prepared in an yet another alternative method by treating 2 with DMF-DMA to yield 5 followed by Vilsmeier-Haack formylation of the latter.