- An Efficient Synthesis of Substituted Pyrazoles from One-Pot Reaction of Ketones, Aldehydes, and Hydrazine Monohydrochloride
-
An efficient, one-pot and metal-free process for the preparation of 3,5-disubstituted and 3,4,5-trisubstituted pyrazoles on multi-gram scale was developed. One-pot condensation of ketones, aldehydes and hydrazine monohydrochloride readily formed pyrazoline intermediates under mild conditions. Oxidation of pyrazolines, in situ, employing bromine afforded a wide variety of pyrazoles. The methodology offers a fast, and often chromatography-free protocol for the synthesis of 3,4,5-substituted pyrazoles in good to excellent yields. Alternatively, a more benign oxidation protocol affords 3,5-disubstituted or 3,4,5-trisubstituted pyrazoles by simply heating pyrazolines in DMSO under oxygen.
- Lellek, Vit,Chen, Cheng-Yi,Yang, Wanggui,Liu, Jie,Ji, Xuebao,Faessler, Roger
-
supporting information
p. 1071 - 1075
(2018/02/26)
-
- 1,3-Diketones from acid chlorides and ketones: A rapid and general one-pot synthesis of pyrazoles
-
1,3-Diketones were synthesized directly from ketones and acid chlorides and were then converted in situ into pyrazoles by the addition of hydrazine. This method is extremely fast, general, and chemoselective, allowing for the synthesis of previously inaccessible pyrazoles and synthetically demanding pyrazole-containing fused rings.
- Heller, Stephen T.,Natarajan, Swaminathan R.
-
p. 2675 - 2678
(2007/10/03)
-
- Utility of cyano acid hydrazide in heterocyclic chemistry: A new route for the synthesis of new 1,2,4-triazolo[1,5-a]pyridines and 1,2,4-triazolo[1,5-a]isoquinolines
-
Cyano acid hydrazide 1 was condensed with cyclohexanone in refluxing ethanolic piperidine to yield the hydrazone 4. Compound 4 reacts with arylidines 5a-i to yield the 1,2,4-triazolo[1,5-a]pyridines 7a-i. Compound 4 also reacts with mixtures of aliphatic aldehydes and different active methylene reagents to yield 1,2,4-triazolo[1,5-a]pyridines 8a-d. Similarly reaction of 4 with arylazomalononitrile to yield the triazolopyridines 10a-d. Reaction of 4 with aromatic aldehydes gives 12a-e. Compound 8a reacts with elemental sulfur to yield the thieno-1,2,4-triazolopyridine 13. This underwent cycloaddition with acrylonitrile, ω-nitrostyrene, chalcone, N-phenylmalemide, dimethylacetylenedicarboxylate and tetracyanoethylene yielding the isoquinolines 15-18. All new compounds have been characterized by their IR, 1H NMR and mass spectra.
- Hussein, Abdel Haleem Mostafa
-
p. 488 - 494
(2007/10/03)
-