Pyrano pyrazol-6-ones

Litvinov YM, Shestopalov AA, Rodinovskaya LA, Shestopalov AM (2009) New convenient four-component synthesis of 6-amino-2,4-dihydropyrano 2,3-c pyrazol-5-carbonitriles and one-pot synthesis of 6 -aminospiro (3H)-indol-3,4 -pyrano 2,3-c pyrazol -(lH)-2-on-5 -carbonitriles. J Comb Chem 11 914—919... 

In the case of 5-bromo-3,4-dimethyl-l-phenyl-l/f, 6//-pyrano[2,3-c]pyrazol-6-one (59), mixed acid nitration results not only in para substitution in the phenyl ring, but also in ipso attack at the 5-position to yield... 

The Pd-catalysed Miyaura-Suzuki coupling of aryltrifluoroborates with 4-tosyloxycoumarins in aqueous conditions offers an attractive route to 4-arylcoumarins <06TL1525> and 4-hydroxycoumarins have been converted into a mixture of predominantly thiopyrano[5, 4 3,4]- pyrano[5,6-c]coumarins and [6,5-c]chromones in a one-pot tandem Knoevenagel - HDA sequence with an S-prenylated 1-phenyl-lff-pyrazole-4-carbaldehyde <06TL2265>. The benzopyrano[4,3-c]benzopyranone system can be obtained from 3-aryl-4-methylcoumarins by deprotonation of the methyl function and subsequent elaboration <06TL5909>. 

Many reports of fused-pyrazole heterocycles have been published. A high throughput synthesis of pyrazolopyrimidines has been achieved by copper(I)-catalyzed cyclizations <05H(65)1821>. A simple synthesis of 6-phenylpyrano[2,3-c]pyrazol-4(lf/)-ones has been reported <05S2583>. A solvent-free, one-pot synthesis of pyrano[2,3-c]pyrazole derivatives in the presence of potassium fluoride and grinding has been disclosed <05SC2509>. Reactions of... 

However, when 36 was heated with a-amino heterocycles or with cyclic 1,3-dicarbonyl or potential 1,3-dicarbonyl compounds, 3-heteroarylp)rr-azol derivatives were obtained. In this manner 36 afforded, when heated with 2-aminopyridine and 3-amino-lH-pyrazol in acetic acid under reflux for 2 h and 5 h, respectively, 3-(5-ethoxy-l-phenyl-lH-pyrazol-3-yl)-4H-pyrido[l,2-fl]pyrimid-4-one (38) and 6-(5-ethoxy-l-phenyl-lH-p5rrazol-3-yl)pyrazolo[l,5-fl]pyrimid-7(lH)-one (39) in 70% and 77% 5deld, respectively. Similarly, 36 afforded with cyclicjS-dicarbonyl compounds, such as 4-hydroxy-6-methyl-2H-pyran-2-one and 5,5-dimethylcyclohexane-l,3-dione by heating in acetic acid for 4 h and 8 h, respectively, the corresponding 3-(5-ethoxy-l-phenyl-lH-pyrazol-3-yl)-7-methyl-2H,5H-pyrano[4,3- 7]pyran-2,5-dione (40) and 3-(5-ethoxy-l-phenyl-IH-pyrazol-3-yl)-7,7-dimethyl-7,8-dihydro-2H-chromene-2,5-dione (41) in 26% and 82% yield, respectively (Scheme 15). 

A key intermediate in a vitamin Bn synthesis, methyl (S)-4-cyano-5,5-dimethyl-6-heptynoate [1123], and a 6-cyano-lH-pyrano[2,3<]pyrazol-4-one derivative [1124] have both been prepared from their carbaldoximes by dehydration with p-tosyl chloride in yields of 88% and 91%, respectively. 

N. J. Pannar, H. A. Barad, B. R. Pansuriya, N. P. Talpada, RSC Adv. 2013, 3, 8064—8070. A highly efficient, rapid one-pot synthesis of some new heteroaryl pyrano[2,3-c]pyrazoles in ionic liqnid nnder microwave-irradiation. 

Sodium hydroxide Pyrano[2,3-c]pyrazol-3-ones from 4-(y-halogenopropyl)-3,5-pyrazolidiones 3,5-Pyrazolidiones from a-dicarboxylic acids via a-dicarboxylic acid chlorides... 

Keywords Isatins, malononitrile, 2-pyrazolin-5-ones, sodium bicarbonate, grinding, room temperature, solvent-free, one-pot multicomponent reaction, heterocycles, spiropyranyl-oxindoles, spiro[indoline-3,4 (l// )-pyrano-[2,3-c]pyrazol]-2-ones... 

Keywords Hydrazines, isatins, p-keto esters, malononitrile, ethyl cyanoacetate, piperidine, ethanol, room temperature, ultrasound irradiation, one-pot multicomponent synthesis, spiro[indoline-3,4 -pyrano[2,3-c]pyrazole] derivatives... 

It was reported [139] that the one-pot two-step reaction of 3-keto esfers with arylhydrazines and then with styrenes and paraformaldehyde in glycerol afforded pyrano[2,3-c]pyrazoles 157 (Scheme 95). 

An efficient one-pot, four-component reaction of hydrazine derivatives 37, p-keto ester 33, isatins 20, and malono-nitrile 3 leading to the S5nthesis of spiro[indoline-3,4 -pyrano[2,3-c]pyrazole derivatives 38 catalyzed by L-proline in water under heating conditions with good yields has recently been reported by Yu et al. [121] (Scheme 20). 

An eco-friendly green approach for the synthesis of substituted pyrano[2 -c]pyrazoles (45) has recently been developed via a multicomponent one-pot approach in aqueous ethanol medium under totally noncatalytic conditions (Scheme 29) [134]. 

V. Colotta, D. Catarzi, F. Varano, F. Melani, G. Filacchioni, L. Cecchi, L. Trincavelli, C. Martini, A. Lucacchini, Synthesis and A1 and A2A adenosine binding activity of some pyrano[2,3-c]pyrazol-4-ones, 11 Farmaco 53 (1998) 189-196. 

H. Kiyani, H.A. Samim, F. Ghorbani, S. EsmaieU, One-pot, four-component synthesis of pyrano[2,3-c]pyrazoles catalyzed by sodium benzoate in aqueous medium, Curr. Chem. Lett. 2 (2013) 197-206. 

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