Facile synthesis of 4-((5-substituted-1H-indol-3-yl)methyl)-3-methyl-1-phenyl-1H-pyrazol-5-ols by selective reduction
- Vol.58B(9), Sep
- New Delhi CSIR 2019
- 1042-1048p.
5-Bromo-1H-indole-3-carbaldehyde (1a) has been condensed with 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one (2) in ethanol containing L-Proline as a catalyst at RT in just 0.5 h to form the Knoevenagel condensation product 3a, i.e., (Z)-4-((5-bromo-1H-indol-3-yl)methylene)-3-methyl-1-phenyl-1H-pyrazol-5(4H)-one. The latter undergoes chemoselective reduction with sodium borohydride in methanol at RT, in just 5 min, to give the title compound 4a, i.e., 4-((5-bromo-1H-indol-3-yl)methyl)-3-methyl-1-phenyl-1H-pyrazol-5-ol. The reactions are found to be general and have been extended to other derivatives of 1 leading to various 3 and 4. Both the reactions i.e. condensation and subsequent reduction, have many advantages like shorter reaction times, good yields of the products formed, and isolation of the products without the need for column chromatography.