Regiochemical Control of Pyrazoles by Solvent and β‐Enamino Diketone Structure: Regioselective Synthesis of 4, 5‐Disubstituted N‐Phenylpyrazoles. Issue 5 (13th March 2017)

• Record Type: Journal Article
• Authors: Souza, Thiago F.; Silva, Michael J. V.; Silva, Raí G. M.; Gonçalves, Davana S.; Simon, Paula A.; Jacomini, Andrey P.; Basso, Ernani A.; Moura, Sidnei; Martins, Marcos A. P.; Back, Davi F.; Rosa, Fernanda A.
• Is Part Of: Asian journal of organic chemistry. Volume 6:Issue 5(2017)
• Page Start: 627
• Page End: 633
• Publication Date: 2017-03-13
• Subjects: cyclization -- ketones -- nitrogen heterocycles -- regioselectivity -- solvent effects; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; 547.005
• DOI: 10.1002/ajoc.201700048
• Languages: English
• ISSNs: 2193-5807

Abstract

Abstract: A simple method for the regiocontrolled synthesis of the 4, 5‐disubstituted N ‐phenylpyrazole regioisomers2 and3 from β‐enamino diketones and phenylhydrazine is described. Pyrazole2 was prepared regioselectively by carrying out the reaction in a protic solvent, whereas pyrazole3 was obtained as the main product by using an aprotic solvent. Steric factors regarding the β‐enamino diketones also influenced the regiochemistry of2 and3 . The influence of solvent on the reaction outcome can be rationalized by using Fukui indices. The structures of2 and3 were unambiguously elucidated by 1 H and 13 C NMR spectroscopy, two‐dimensional HMBC experiments, high resolution mass spectrometry, and X‐ray crystallographic analysis. Abstract : This way or that ! A regiocontrolled synthesis of 4, 5‐disubstituted N ‐phenylpyrazoles from unsymmetrical β‐enamino diketones in either protic or aprotic solvent has been developed. A series of regioisomers of 4, 5‐disubstituted N ‐phenylpyrazoles have been prepared this way.