Methyl carbonium ion migration during the reaction of 4-chloro-5-methoxyl-3(2H)-pyridazinone with trifluoroethylation agents.
To synthesize 4-chloro-5-methoxy-2-(b-trifluoroethyl)-3(2H)-pyridazinone (4), the reactions of 4-chloro-5-methoxy-3(2H)-pyridazinone (5) with RCH(2)CF(3)(R = I, TsO, MsO, TfO) in different solvents were studied. It was found that methyl group migration took place during this reaction. An oxonium salt 9 was suggested as the active intermediate for the formation of the byproduct 4-chloro-5-methoxy-2-methyl-3(2H)-pyridazinone (7) and 4-chloro-2-methyl-5-(b-trifluoroethoxy)-3(2)-pyridazinone(8).
Li
Qin
Q
The State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, Beijing, PR China. liqin@bjmu.edu.cn
Lin
Guichun
G
Liu
Li
L
Yang
Zhenjun
Z
Zhang
Li-He
LH
D000431:Ethanol / Q000737:chemistry; D005461:Fluorine / Q000737:chemistry*; D007477:Ions / Q000737:chemistry*; D015394:Molecular Structure; D011724:Pyridazines / Q000737:chemistry*; D012492:Salts / Q000737:chemistry
D007477:Ions; D011724:Pyridazines; D012492:Salts; D005461:Fluorine; D000431:Ethanol