Pyrazolo pyrazolone

Pyrazolo[3,4-d][l,2]diazepines synthesis, 7, 597 Pyrazolop, 4- 6][ 1,4]diazepines synthesis, 5, 272 Pyrazolo[l, 4]diazepinones as anticonvulsant, 1, 170 Pyrazolo[2,3-e]diazepinones synthesis, 5, 272 1 H-Pyrazolo[l,5-6]imidazoles synthesis, 6, 992 Pyrazolo[2,3-a]imidazoles biological activity, 6, 1024 Pyrazolo[2,3-c]imidazoles reactions, 6, 1041 synthesis, 6, 1047 Pyrazolo[2,3-imidazoles synthesis, 6, 991 Pyrazolo[3,2- njisoquinolines synthesis, 5, 339 Pyrazolop, 4-c]isoquinolines synthesis, 5, 273 Pyrazolonaphthyri dines synthesis, 5, 339 Pyrazolone, diazophotolysis, 5, 252 Pyrazolone, 4,4-dihalo-rearrangements, 5, 250 Pyrazolone, ethoxy-hydrazinolysis, 5, 253 Pyrazolone, 4-halo-... 

In an extension of previous work on conjugated enamine carbonyl derivatives, reaction of the pyrazolone 91 with IV.lV-disubstituted hydrazines on heating in an alcohol solvent afforded the hexahydropyrazolo[4,3-Michael-type addition of the alcohol to a pre-formed pyrazolo-diazepine, was excluded <06T8126>. 

Pyrazolone-1,2-dioxides 311 were subjected to cycloaddition with a wide range of olefinic compounds leading to the 0-2,3,3 ,4-tetrahydro-pyrazolo[l,5-3]isoxazole cycloadducts 312. The behavior of these reactive species 311 toward unsaturated compounds, stereochemical and mechanistic aspects, were discussed in details (Equation 134) <1994J(P2)1337>. 

Pyrazoles, 13 599 Pyrazolinone couplers, 19 254-255 Pyrazolo-(3,2,-c)-5-triazole couplers, 19 256 Pyrazolobenzimidazole couplers, 19 256 Pyrazolone dyes, 19 285 Pyrazolone Orange, 19 435 pigment for plastics, 7 367t Pyrazolone reds, 19 437 Pyrazolones, 9 283 13 599... 

The reaction of 3-methyl-5-pyrazolone with diethyl 2-acylmalonates at 140-150°C for 2 hr afforded pyrazolo[5,l-ft]oxazine-6-carboxylates (1665) in 22-64% yields [77JAP(K)77089],... 

Besides uracil-6-iminophosphorane, the iminophosphorane component was extended to pyrazole 3 and pyrazolon-4-iminophosphoranes 363 (94JOC3985). In its electron distribution, 363 can be compared with uracil 346. With arylisocyanates, pyridine, or y-picoline, zwitterionic pyrazolo [3, 4 4,5]pyrido[6,l-a]pyrimidines (364) are obtained and with isoquinoline, 365 is formed (Scheme 131). Again, both systems show a typical negative solvatochromism (94JOC3985). 

The reaction of pyrazolones (207) with 3-oxo-esters gives mainly the pyrazolo[l,2-a]pyrazol-l,5-(lff,5//) diones (208). However, with 207 (R = Ph), only oxazines 209 are obtained. Thermal and photochemical isomerization of 204 gives 209 (84CPB930, 84JAP59128384). Phenace-tylpyrazole (210) is cyclized to 211 with thiophosgene (84JOC3672). 

The reaction of 1,3-dicarbonyl compounds with 3-amino-5-pyrazolones has been used extensively in the preparation of pyrazolo[3,4-b]pyridines. A number of products are possible, depending on the reagent used and the direction of cyclization. As a consequence, many of the early reports proposed incorrect structures. 

Cyclization of a 1-substituted 3-amino-5-pyrazolone or its 5-amino isomer produces 2- or 1-substituted pyrazolo[3,4-b]pyridones, respectively. Alternative reaction at N-2 to form a pyrimidine ring has not been reported. 

Michael-type condensation of cyanoacetohydrazide (NCCH2CONHNH2, CAH) with 1,3-dicarbonyl compounds gave pyrazolo[3,4-b]pyridines under certain conditions. With l,l,l-trifluoropentane-2,4-dione in the presence of piperidine a 1 3 mixture of pyrazolone 92a and the expected aminopyridone 91a was obtained.15 The bicycle was also obtained from hydrazone (90) or by thermal reaction between its two precursors.32 Reaction of CAH and / -keto aldehydes gave good yields of only bicyclic products 92b,20 whereas ethyl benzoylacetate in the presence of piperidine gave bicycle 92c (Ar = Ph)... 

A number of reduced pyrazolo[3,4-c]pyridines have been prepared by cyclization of 3-piperidones substituted in the 4-position. For example, reaction of 4-ethoxycarbonyl- or 4-cyano-3-piperidones (125 X = C02Et or CN) with hydrazine afforded the pyrazolones 126a (R1 = H)119 or amines 127,120 respectively. 

The product of the reaction of 3-methyl-l-phenyl-5-pyrazolone with chloride 21c in ethanol in the presence of sodium ethoxide was assigned structure 232 (83MI1). Neither spectral nor elemental analysis data were given to support such an ambiguous assignment, however. As the 5-pyrazolone derivative is an active methylene compound, its reaction with hydrazonoyl halides 21c is expected to give pyrazolo[3,4-c]pyrazole derivative 233, not 232. 

The most commonly used magenta couplers are l-aryl-5-pyrazolones 32, patented in 1934 [40], The principles for their design and use are the same as that for yellow couplers. In recent years other classes of heterocyclic couplers have been developed. 1/7-Pyrazolo[3,2-c]-l,2,4-triazole couplers 33 and the isomeric 1H-pyrazolo[l,5-6]-l,2,4-triazole couplers have become important because of their sharp absorptions in the green region and their ability to couple efficiently over a wide pH range [41 15],... 

Treatment of l-acyl-3-amino-5-pyrazolones (417) with an equimolar amount of an enol ether, such as ethoxymethylenecyanoacetate or ethoxymethylenemalononitrile in DMSO at 70-80 C for 3 h furnishes pyrazoleacrylonitriles (418) in good yields. The use of other solvents decreases the yields considerably. Heating the intermediates (418) in diphenyl ether at 200 °C promoted cyclization to give 2-acyl-6-amino-3-hydroxy-2//-pyrazolo[3,4-b]pyridines (419) (Scheme 47) <94JHC925>. 

The pyrazolo[4,3-e][l,2,5]oxadiazin-3-ones (163) are formed by the action of phosgene or ethyl chloroformate on the aminonitrosopyrazoles (162) (Equation (22)). They have been used as intermediates in peptide synthesis <761ES70). A pyrazolo[4,3-e][l,3,4]oxadiazine (165) is formed together with a pyrazolotriazine (166) (Equation (23)) by the reaction of the phenylhydrazone of a pyrazolone (164) with cyanogen bromide <85JCS(P1)1499>. 

A standard pyrazolone preparation applied to piperidone esters is shown in Scheme 109 (34JA700). Standard procedures for the preparation of saturated and partially unsaturated pyrazolo[l,2-a]pyridazines are shown in Schemes 110 (68BSF4222), 111 (70CPB1526) and 112 <65CR(261)1872). 

Pyrazolo[l,5-i]isoxazoles were prepared by cycloaddition of pyrazolone jV,iV-dioxides with electron-rich alkenes <94JCS(P2)1337>. In general, mixtures of diastereomeric regioisomers are obtained, with the predominant formation of exo cycloadducts. The l-methyl-2-aminoindazolium salt (164) reacted with acetylacetone in the presence of triethylamine to give the pyrazolo[2,3-Z)]indazole derivative (76), which was oxidized with lead tetraacetate to give (77) (Section 8.04.6.1) <76CPB2267>. 

Condensation of 403 with aromatic aldehydes in the presence of ZnCl2 produced the corresponding 4-arylidenepyrazole derivatives 404 in 50-75% yield after 5-8 h heating at 140-150 °C. However, when the reaction was done under MWI for 5-7 min, the products were identified as l/f-pyrazolo[3,4-Z)]quinolines 405 and not 404 albeit in lower yields (40-71%) (Scheme 81) (00MI4). Reaction of 407 with pyrazolones 406 gave 408 (99SC4403). 

Kobayashi and co-workers successfully achieved the asymmetric 1,3-dipolar cycloaddition reaction of azomethine imines with terminal alkynes catalyzed by CuHMDS and DIP-BINAP ligand to provide N,N-bicyclic pyrazolidinone derivatives in high yields with exclusive regioselectivity and excellent enantioselectivity (Scheme 26) [46]. Mechanistic studies elucidated a stepwise reaction pathway and revealed that the steric character of the ligand determines the regioselectivity. Arai and co-workers applied chiral bis(imidazolidine)pyridine-CuOAc complex to the [3+2]cycloaddition of azomethine imines with propiolates for the construction of bicyclic pyrazolo[l,2-a]pyrazolone derivatives with up to 74% ee [47]. 

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