ChemInform Abstract: Reaction of Aroyl-Substituted Heterocyclic Ketene Aminals with Nitrile Imines:...
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2000 pyrazole derivatives pyrazole derivatives R 0180 02 - 149 Reaction of Aroyl-Substituted Heterocyclic Ketene Aminals with Nitrile Imines: An Efficient Synthesis of Fully Substituted Pyrazoles and Evidence of Nucleophilic Addition of Enamines to 1,3-Dipoles. — Cycloaddition of heterocyclic aminals such as (I) and (IV) with the nitrile imine (II) affords the fully substituted pyrazoles (III) and (V). The reaction proceeds stepwise by nucleophilic addition forming a hydrazone intermediate and subsequent cyclization. In the case of nitrile imine (VII), hydrazones are obtained as the sole products. They can be cyclized to the corresponding pyrazoles, e.g. (IX), only under drastic conditions. — (LIU, BO; WANG, MEI-XIANG; HUANG, ZHI-TANG; Tetrahedron Lett. 40 (1999) 41, 7399-7402; Inst. Chem., Chin. Acad. Sci., Beijing 100080, Peop. Rep. China; EN) 1
Transcript of ChemInform Abstract: Reaction of Aroyl-Substituted Heterocyclic Ketene Aminals with Nitrile Imines:...
2000 pyrazole derivatives
pyrazole derivativesR 0180
02 - 149Reaction of Aroyl-Substituted Heterocyclic Ketene Aminals withNitrile Imines: An Efficient Synthesis of Fully Substituted Pyrazolesand Evidence of Nucleophilic Addition of Enamines to 1,3-Dipoles.— Cycloaddition of heterocyclic aminals such as (I) and (IV) with the nitrileimine (II) affords the fully substituted pyrazoles (III) and (V). The reactionproceeds stepwise by nucleophilic addition forming a hydrazone intermediateand subsequent cyclization. In the case of nitrile imine (VII), hydrazones areobtained as the sole products. They can be cyclized to the correspondingpyrazoles, e.g. (IX), only under drastic conditions. — (LIU, BO; WANG,MEI-XIANG; HUANG, ZHI-TANG; Tetrahedron Lett. 40 (1999) 41, 7399-7402;Inst. Chem., Chin. Acad. Sci., Beijing 100080, Peop. Rep. China; EN)
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