1,2-Addition to trifluoromethylated β-enamino diketones: regioselective synthesis of trifluoromethyl-containing azomethine pyrazoles and isoxazoles

A simple and efficient methodology for highly regioselective synthesis of azomethine pyrazoles and isoxazoles containing a trifluoromethyl group is reported. The cyclocondensation of trifluoromethylated β-enamino diketones (TBED) with phenylhydrazine and hydroxylamine hydrochloride, in the presence...

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Published in:Organic & biomolecular chemistry 2020-04, Vol.18 (13), p.2524-2537
Main Authors: Pianoski, Karlos Eduardo, Poletto, Julia, Vieira da Silva, Michael Jackson, Ascencio Camargo, Jeniffer Nascimento, Jacomini, Andrey Petita, Gonçalves, Davana Silva, Back, Davi Fernando, Moura, Sidnei, Rosa, Fernanda Andreia
Format: Article
Language:English
Subjects:
Amines
Aromatic compounds
Crystallography
Diketones
Hydroxylamine
Organic compounds
Pyrazoles
Regioselectivity
Synthesis
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Summary:A simple and efficient methodology for highly regioselective synthesis of azomethine pyrazoles and isoxazoles containing a trifluoromethyl group is reported. The cyclocondensation of trifluoromethylated β-enamino diketones (TBED) with phenylhydrazine and hydroxylamine hydrochloride, in the presence of BF 3 , provided 5-aryl-4-[( tert -butyl)iminomethyl]-3-trifluoromethylazoles by aza-Michael-type 1,2-addition. The scope of the reaction was expanded by transimination with arylamines in a one-pot method starting from TBED. Thus, 83 novel 4-[(alkyl/aryl)iminomethyl]-3-trifluoromethylazoles were obtained with high regioselectivity and in yields of 51 to 89%. Trifluoromethylated β-enamino diketones undergo type 1,2-addition leading to regioselective synthesis of trifluoromethylated azoles containing an azomethine group.
ISSN:1477-0520
1477-0539
DOI:10.1039/d0ob00319k