A general method for the preparation of 3-acyl-4-cyano-5-amino-pyrazoles

Tetrahedron Letters

Volumn 47, Issue 32, 2006, Pages 5797-5799

  Ge, Min ^a   Cline, Eric ^a   Yang, Lihu ^a  

^a MERCK RESEARCH LABORATORIES   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

PYRAZOLE DERIVATIVE;

ARTICLE; CHEMICAL MODIFICATION; CHEMICAL REACTION KINETICS; DRUG HYDROLYSIS; DRUG SYNTHESIS; STEREOCHEMISTRY;

EID: 33745612700     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.tetlet.2006.05.173     Document Type: Article

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11. This strategy has been used for the synthesis of 3-aryl-5-amino-pyrazoles, where pre-formed methyl enol ether led to the facile formation of the desired pyrazoles. See:. Hanefeld U., Rees C.W., White A.J.P., and Williams D.J. J. Chem. Soc., Perkin Trans. 1 (1996) 1545-1552
12. We are not certain about the identity of the intermediate because both vinyl chloride 3 and compound 3a can lead to the corresponding enol ether 4 after methanol treatment. This intermediate is too unstable to be isolated. However, there is one report supporting vinyl chloride as the intermediate. See:. Friedrich K., and Thieme H.K. Synthesis 5 (1973) 111 {A figure is presented}
13. The enol ether 4 is quite stable under acidic conditions but quickly decomposes under basic conditions.
14. 6) 172.1, 158.2, 112.2, 111.8, 64.9, 63.8, 14.1.
15. +] 223.1, found 223.1.