A facile synthesis of pyrazoles with multi-point structural diversity by 1,3-dipolar cycloaddition |
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Authors: | Kwai Ming J. Cheung |
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Affiliation: | Cancer Research UK Cancer Therapeutics Unit, The Institute of Cancer Research, 15 Cotswold Road, Sutton, Surrey, SM2 5NG, UK |
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Abstract: | We describe the synthesis of diverse pyrazoles by 1,3-dipolar cycloaddition of ethyl diazoacetate with various acetylenes in refluxing toluene. The product pyrazoles are useful starting points for preparing a diverse collection of trisubstituted pyrazole carboxamides. For aryl and heteroaryl alkynes a single product is obtained while alkyl alkynes afford a ca. 6:1 mixture of regioisomers. The observed regioselectivity for the cycloaddition step and the ease of reaction are consistent with predictions derived from computing the HOMO-LUMO energies of the reactants. |
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Keywords: | Pyrazole 1,3-Dipolar cycloaddition HOMO-LUMO |
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