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Unexpected Reaction Course of 3‐Amino‐5‐aryl‐1H‐pyrazoles with Dialkyl Dicyanofumarates
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Titel: |
Unexpected Reaction Course of 3‐Amino‐5‐aryl‐1H‐pyrazoles with Dialkyl Dicyanofumarates |
In: | Helvetica Chimica Acta, 96, 2013, 4, S. 633-643 |
veröffentlicht: |
Wiley
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Umfang: | 633-643 |
ISSN: |
0018-019X 1522-2675 |
DOI: | 10.1002/hlca.201200633 |
Zusammenfassung: | <jats:title>Abstract</jats:title><jats:p>On treatment of 3‐amino‐5‐aryl‐1<jats:italic>H</jats:italic>‐pyrazoles <jats:bold>1</jats:bold> with dialkyl dicyanofumarates (=(<jats:italic>E</jats:italic>)‐but‐2‐enedioates) <jats:bold>4</jats:bold> in boiling 1,2‐dichloroethane, two competitive reactions occurred leading to 3‐aryl‐5‐cyano‐6,7‐dihydro‐6‐oxo‐1<jats:italic>H</jats:italic>‐pyrazolo[3,4‐<jats:italic>b</jats:italic>]pyridine‐4‐carboxylates <jats:bold>10</jats:bold> and 7‐amino‐2‐arylpyrazolo[1,5‐<jats:italic>a</jats:italic>]pyrimidine‐5,6‐dicarboxylates <jats:bold>11</jats:bold>. In DMF at room temperature, as well as at 100°, only compounds <jats:bold>10</jats:bold> were isolated. The formation of the major products of type <jats:bold>10</jats:bold> was rationalized <jats:italic>via Michael</jats:italic> addition of <jats:bold>1</jats:bold> as a <jats:italic>C</jats:italic>(<jats:italic>4</jats:italic>)‐nucleophile onto <jats:bold>4</jats:bold>, followed by HCN elimination and lactamization. On the other hand, the minor products <jats:bold>11</jats:bold> result from a <jats:italic>Michael</jats:italic> addition of <jats:bold>1</jats:bold> onto <jats:bold>4</jats:bold> <jats:italic>via</jats:italic> the NH<jats:sub>2</jats:sub> group, and subsequent HCN elimination and cyclization. The structures of the products have been established by X‐ray crystallography.</jats:p> |
Format: | E-Article |
Quelle: | Wiley (CrossRef) |
Sprache: | Englisch |