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Gill A, Werz UR, Maas G. N-vinylation and N-allylation of 3,5-disubstituted pyrazoles by N–H insertion of vinylcarbenoids. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES 2015. [DOI: 10.1515/znb-2015-0115] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
A vinylcarbenoid approach toward N-functionalization of NH-pyrazoles is presented. The rhodium(II)-catalyzed reaction of methyl styryl-diazoacetate (1) or dimethyl 2-diazoglutaconate (3) with 3,5-disubstituted pyrazoles gave products of carbenoid N–H insertion in high combined yields, although regioselectivity issues posed by the pyrazole or the vinylcarbenoid moiety as well as positional and configurational isomerism concerning the C,C double bond of the latter led to product mixtures. The ambident reactivity of the vinylcarbenoid derived from 1 could be steered by the catalyst: while Rh2(OAc)4 yielded products of direct carbenoid insertion preferentially, silver(I) catalysis strongly favored reaction at the vinylogous site of the carbenoid resulting in an N-allylation of the pyrazoles.
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Affiliation(s)
- Agagia Gill
- Institute of Organic Chemistry I, University of Ulm, 89081 Ulm, Germany
| | - Udo R. Werz
- Institute of Organic Chemistry I, University of Ulm, 89081 Ulm, Germany
| | - Gerhard Maas
- Institute of Organic Chemistry I, University of Ulm, 89081 Ulm, Germany
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