Journal
TETRAHEDRON LETTERS
Volume 47, Issue 15, Pages 2531-2534Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.tetlet.2006.02.053
Keywords
3-amino-5-(pyrid-2-yl)-1H-pyrazole; electrophilic substitution; regiochemistry; crystal structure
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Funding
- Engineering and Physical Sciences Research Council [GR/S12883/01] Funding Source: researchfish
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An improved synthesis of 3{5}-amino-5{3}-(pyrid-2-yl)-1H-pyrazole (1) is described, which affords the compound on a multi-gram scale. Reaction of I with acid chloride and isothiocyanate electrophiles in MeCN cleanly results in attack at its amino group, yielding N-(3-{pyrid-2-yl}-1H-pyrazol-5-yl)amide and N-(3-{pyrid-2-yl}-1H-pyrazol-5-yl) thiourea products. These are good candidates as proligands for the simultaneous complexation of metal cations and anions. However, treatment of I with isocyanates under the same conditions instead yields attack at the pyrazole ring, giving 3-(pyridin-2-yl)-5-aminopyrazole-l-carboxylic acid amides as the only isolable products. The differing regiochemistries of these reactions were confirmed by H-1 NMR and X-ray crystallography. (c) 2006 Elsevier Ltd. All rights reserved.
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