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7540493 
Journal Article 
Microwave Assisted Vilsmeier-Haack Reaction on Substituted Cyclohex-anone Hydrazones: Synthesis of Novel 4,5,6,7-Tetrahydroindazole Derivatives 
Kaur, AK; Bala, R; Kumari, P; Sood, S; Singh, K; , 
2019 
1 
Letters in Organic Chemistry
ISSN: 1570-1786 
BENTHAM SCIENCE PUBL LTD 
SHARJAH 
170-175 
WOS:000458302100003 
Vilsmeier-Haack reaction is one of the most important chemical reactions used for formylation of electron-rich arms. Even though Vilsmeier-Haack reaction was studied on a wide variety of hydrazones of enolizable ketones, literature lacks the examples of the use of 4-substituted cyclohexanones as a substrate. The cyclization potential of hydrazones of cyclic keto compounds is still interested topic of investigation. In the present study, the reaction of various hydrazines with 4-substituted cyclohexanones was proceeded and the resulted hydrazones in crude form were treated with Vilsmeier-Haack reagent using both conventional as well as microwave methods. The reaction of phenyl hydrazine with 4-phenylcyclohexanone yielded the corresponding tetrahydro-1H-carbazole instead of hydrazone during solvent evaporation at 40 degrees C. By keeping the temperature of water bath to 0 degrees C, the corresponding hydrazone was isolated in crude form which was immediate treated with POC1(3)/DMF for 10 min at 90 degrees C using microwave irradiation method afforded novel 4,5,6,7-tetrahydroindazole derivative. Using this optimized condition, the substrate scope for the synthesis of tetrahydroindazole derivatives was explored and synthesized total 6 final compounds. The microwave assisted synthesis of tetrahydroindawles from 4-substituted cyclohexanones has been reported for the first time under mild conditions in good yield. Easy work up procedure, high yielding, shortened reaction times, clean and ecofriendly are the main advantages of this protocol.