Nitrogen, heterocyclic compounds pyrazole

A second method of producing pyrazole-containing compounds was described by Olivera et al. [51] and involves the use of an enaminoketone (41) (Scheme 5). The initial amine-exchange/heterocyclization produced pyrazole tautomers, so another method was attempted with NT NHMe. However, two isomers were produced with the methyl group on either nitrogen. Compound 42 was formed in 55% yield. 

Two independent papers have reported the synthesis of nitrogen-heterocycle complexes of the type [RhCl3(py-X)3] (py-X = 3-Etpy, 3-CNpy, 4-Etpy, or 4-CNpy) and rr(ans-[RhY2L4] (Y = Cl or Br L = several substituted pyridines, isoquinoline, pyrimidine, pyrazole, thiazole, and substituted imidazoles). All the compounds were prepared catalytically by boiling RhCl3.3H20 with ethanolic solutions of L. It is interesting that 2-substituted... 

Inventing heterocycles by further replacement of CH groups by nitrogen in pyrrole leads to two compounds, pyrazole and imidazole, after one replacement and to two triazoles after two replacements. 

The synthesis of 3-dimethyl-2-benzoyl propenenitriles l(a-b) is the vital key intermediate for the synthesis of various nitrogen heterocycles, such as pyrazole and pyrimidine derivatives. The literature reports suggest that 1,3,4-trisubstituted pyrazole derivatives are important compounds in the preparation of 1,5-diphenylpyrazole nonnudeoside derivatives, which are used as HIV-1 normucleoside reverse transcriptose inhibitors [15]. Similarly, 4-cyano pyrazole... 

Of the heterocyclic nitrogen-containing compounds, a-phenylindole is used to stabilize latex polymers and copolymers of vinyl chloride [99]. Melamine has foimd use for the stabilizing of suspension polymers, where a-phenylindole proves inactive [63]. Derivatives of morpholine [274], symmetrical triazine [275], pyrazole [276], as well as derivatives of imidazole, imidazoline, oxazole, oxazoline, thiazole, and thiazoline [277] are recommended in the patent literature for stabilization. 

The heterocyclic compound (6) is obtained by the action of potassium alkyl-dithiocarbonates with 4-chloro-3,5-dinitrobenzotrifluoride. Nitrogen-containing anions from pyrroles, pyrazoles, and imidazoles have been used to displace... 

The compounds of this article, ie, ftve-membered heterocycles containing two adjacent nitrogen atoms, can best be discussed according to the number of double bonds present. Pyrazoles contain two double bonds within the nucleus, imparting an aromatic character to these molecules. They are stable compounds and can display the isomeric forms, (1) and (2), when properly substituted. Pyrazoles are scarce ia nature when compared to the imidazoles (3), which are widespread and have a central role ia many biological processes. 

The compounds referred to as azolides are heterocyclic amides in which the amide nitrogen is part of an azole ring, such as imidazole, pyrazole, triazole, tetrazole, benzimidazole, benzotriazole, and their substituted derivatives. In contrast to normal amides, most of which show particularly low reactivities in such nucleophilic reactions as hydrolysis, alcoholysis, aminolysis, etc., the azolides are characterized by high reactivities in reactions with nucleophiles within the carbonyl group placing these compounds at about the same reactivity level as the corresponding acid chlorides or anhydrides. 11... 

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