In Situ Generation of Nitrilimines from Aryldiazonium Salts and Diazo Esters: Synthesis of Fully Substituted Pyrazoles under Room Temperature
作者:Ying Shao、Hao Zheng、Junfeng Qian、Xiaobing Wan
DOI:10.1021/acs.orglett.8b00750
日期:2018.4.20
A novel one-pot synthesis for fully substituted pyrazoles has been well developed via the in situ generation of nitrilimines from aryldiazonium salts and diazo esters and a subsequent cycloaddition with 1,3-dicarbonylcompounds. High yields, mild conditions, wide substrate scope, and operational simplicity are the significant advantages of this methodology.
Reactions of arenediazonium chlorides with ethyl 2-methyl-and 2-chloro-4-oxobutanoates gave, respectively, ethyl 2-(arylhydrazono)propanoates and chloro(arylhydrazono)acetates. Ethyl 2-(arylhydrazono)-propanoates reacted with the Vilsmeier-Haak reagent to give ethyl 1-aryl-4-formyl-1H-pyrazole-3-carboxylates. Ethyl 1-aryl-4-acetyl-5-methyl-1H-pyrazole-3-carboxylates were obtained by reaction of chloro(arylhydrazono) acetates with acetylacetone. Reactions of the obtained pyrazole derivatives with hydrazine and methylhydrazine led to the formation of the corresponding 3,4-R(2)(1)-6-R(2)-2-aryl-2,6-dihydro-7H-pyrazolo[3,4-d]pyridazin-7-ones (R(1), R(2) = H, Me) which were subjected to alkylation and sulfurization.
BERNARD, A.;COCCO, M. T.;MACCIONI, A.;PLUMITALLO, A., FARMACO. ED. SCI., 1985, 40, N 4, 259-271
作者:BERNARD, A.、COCCO, M. T.、MACCIONI, A.、PLUMITALLO, A.