1- acetyl-3,5-dimethylpyrazoles

With an activated C—C triple bond two successive additions can occur if the intermediate alkene is reactive enough. DMAD and 3,5-dimethylpyrazole give an initiaj fumarate (255) which reacts further at the other end to form regioselectively the succinates (256). On the other hand, methyl ethynyl ketone reacts twice at the same carbon atom with pyrazole to form 1,1-pyrazolylbutanone (258) (68ZC458). The probable intermediate, a pyrazolide vinylogue (257), can be prepared from methyl chlorovinyl ketone and pyrazole, in a reaction which is similar to acetylation (Section 4.04.2.1.3(x)). 

Kotlyarevsky et al. (69TZV927) showed that ketones that are not substituted on the nitrogen of the ring lead to certain complications. Thus, under normal conditions (60CB593), 4-acetyl-3,5-dimethylpyrazole (6) gave a product containing significant quantities of the respective acetylene derivative 11 and an unexpected chloroacetylene 10. 

Following the data in publications (54TZV803 72ZOB802 74KGS310), which indicate that the vinyl compounds are phosphorylated more readily in benzene than in POCI3, the reaction was carried out in this last solvent. Accordingly, only chlorides 13a, 14a were formed from 4-acetyl-l,3-dimethylpyrazole (12a) in... 

In addition, it was clear that the presented scheme does not exhaust all the possible paths of anomalous chlorination. Thus, 4-acetyl-l,3,5-trimethylpyrazole with 4-5 moles of phosphorus pentachloride gave mainly 4-Q ,/3-dichlorovinyl-5-chloromethyl-l,3-dimethylpyrazole, and its precursor (according to GLC data) was the dichloride. It could be possible that in the case of 4-chlorovinyl derivatives of pyrazole the chlorination at the p position is facilitated by the electron-donating characteristics of the 4-pyrazolyl radical (86TH1). 

The proton spectra of 1-substituted 3-nitropyrazoles [296], 5-substituted 3-methyl-l-aryl-4-nitropyrazoles [297, 298], 1,3- and l,5-diphenyl-4-nitropyra-zoles [281], 5-iodo-4-nitro-l,3-dimethylpyrazole [299], l-methyl-3-nitro-4- and l,3-methyl-4-nitro-5-phenylethynylpyrazoles [300], l-methyl-3-nitro-5-methoxy-carbonylpyrazole [301], l-methyl-3-nitro- and l-methyl-5-nitro-4-cyanopyrazoles [302], A-(2,4-dinitrophenyl)nitropyrazoles [303], a- and [3-anomers of 3-nitro-and4-nitropyrazolyl-l-ribonucleosides [304, 305], 3-substituted 1,5-dimethyl- [306] and 5-substituted l,3-dimethyl-4-nitropyrazoles [279], l-acetyl-3-anilino-4-nitro-5-dimethylaminopyrazoles [307], 3-substituted 4-nitro-5-carboxylic acid derivatives [308, 309], 4-nitropyrazolo[4,3-e][l, 4]diazepin-5,8-diones showing antimicrobial activity [310], l-heteryl-4-nitropyrazole derivatives [311], 3-nitro- and 5-nitro-l-methylpyrazole [312], 4-nitro-5-(trimethylsilyl)pyrazole [313], 3-methyl-4-nitro-pyrazol-5-ones [298], and some other nitropyrazoles [248, 314-320] have been examined. 

Heterocycles. Syntheses are formulated for the preparation of 2,4-dimethyl-3-acetyl-5-carboethoxypyrrole (1) and 3,5-dimethylpyrazole (2). ... 

Hydrazino-3-methoxyquinoxaline has been hydrolyzed to quinoxaline-2,3-dione by treatment with boiling 48% HBr or 2% HCl at 140-150 . A series of 2-hydrazino-3-alkoxyquinoxalines gives 2-(2-acetylhydrazino)-3-alkoxyquinoxalines by reaction with l-acetyl-3,5-dimethylpyrazole, and benzoylation of the methylhydrazino compound 2 similarly yields the benzoyl derivative 3." ... 

The reactions of the completely reduced compounds have attracted much attention because of their close relationship to piperazine. Thus it has been shown, as might be expected, that the 2-position in compounds such as the parent 100 can be readily acetylated and benzoylated" and ureas are formed with phenylisocyanate and phenylisothiocyanate." Compound 100 also reacts at the 2-position with p-acetamidobenzene-sulfonyl chloride to give a sulfonamide. There are several examples of the alkylation of the amine in the 2-position. Various alkyl halides -have been used, as well as ethylene oxide," p-nitrobenzoyl-ethyleneimine, " and l-guanyl-3,5-dimethylpyrazole nitrate. Compound 100 also undergoes the Eschweiler-Clarke modification of the Leuckart reaction to give the 2-methyl compound." ... 

Pyrazoles.- Formation During the formation of 3,5-dimethylpyrazole from acetyl-... 

A soln. of phenol in ligroin heated 20 min. at 115-120° with N-acetyl-3,5-di-methylpyrazole and AIGI3 4-hydroxyacetophenone. Y 69%.—N-Acyl-3,5-dimethylpyrazoles and N-acylimidazoles are much weaker acylating agents than the corresponding acid chlorides. F. e. and limitations s. W. Ried and H.-J. Schubert, A. 653, 181 (1962). 

Acetylation of the isonicotinoylhydrazone of sodium D-glucuronate (which exists in the -pyranose form) gave the 6,1-lactam derivative (31)) the conformation of which was examined in detail. A variety of N-6-D-glucopyranosylated heterocycles have been synthesized by condensation of 2,3,, 6-tetra-O-benzyl-D-glucose hydrazone (which exists as a mixture of ring and chain isomers) with acetyl-acetone [leading to the synthesis of the 3,5-dimethylpyrazole derivative (32)], (ethoxymethylene)malondinitrile, (ethoxymethylene)... 

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