A novel procedure for the preparation of 3-substituted 4-hydroxypyrazole-5-carboxylic acids as an approach to pyrazomycin

Farkaš, J.; Flegelova, Z.

doi:10.1016/s0040-4039(01)97018-2

Cited by 14 publications

(7 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…By condensation of the isomeric mixture 203a and 203b with ethyl hydrazinoacetate hydrochloride, corresponding isomeric hydrazones 204 were obtained, which underwent Dieckmann cyclization to furnish an isomeric mixture of 4-hydroxy pyrazole derivatives 205 , when treated with NaOMe in MeOH under reflux conditions for 3 h (Scheme ) . Similar Dieckmann condensation of α-ketoester 2-carboalkoxymethylhydrazones was reported by Farkaš et al to synthesize corresponding 3-substituted 4-hydroxypyrezole-5-carboxylates in 39–85% yields. Reactions were conducted using NaOEt in refluxing EtOH for 2 h. The starting hydrazones were prepared by treatment of α-oxoesters with hydrazinoacetate derivatives.…”

Section: Synthesis Of N-heterocyclessupporting

confidence: 52%

Chemistry of α-Oxoesters: A Powerful Tool for the Synthesis of Heterocycles

2014

View full text Add to dashboard Cite

Section: Synthesis Of N-heterocyclessupporting

confidence: 52%

Chemistry of α-Oxoesters: A Powerful Tool for the Synthesis of Heterocycles

2014

View full text Add to dashboard Cite

“…In fact, we found that the aldehyde hydrazones (3; R' = Me or Ph, R2 = H, Me, Et, Pr, or Ph) and the glyoxals (4; R3 = H, Me, or Ph), when heated together under anhydrous conditions in butyl acetate containing acetic acid, afforded moderate to excellent yields of the 4-hydroxypyrazoles (2); fourteen representatives of these are listed in Table 1 (entries [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The structural assignment of these rests on (i) agreement in m.p.s [mixed m.p.…”

Section: Resultsmentioning

confidence: 99%

Reactions of glyoxals with hydrazones: a new route to 4-hydroxypyrazoles

Begtrup¹,

Nytoft²

1985

J. Chem. Soc., Perkin Trans. 1

View full text Add to dashboard Cite

“…Cyclization of 16 with sodium methoxide gave the 4-hydroxy pyrazole derivative as a mixture of isomers 17a and 17b (19), which was obtained as a powder after purificaCan. J. Chem.…”

mentioning

confidence: 99%

Syntheses of C-nucleosides. IX. Reactions of D,L-3,4-di-O-isopropylidene-2,5-anhydroallose with Wittig reagents. Syntheses of bis-homo anhydro-C-nucleosides.

Just¹,

Ramjeesingh²,

Liak³

1976

Can. J. Chem.

View full text Add to dashboard Cite

GEORGE .IUST, MOHABIR RAMJEESINGH, and TENG JIAM LIAK. Can. J. Chem. 54, 2940Chem. 54, (1976. The nrnr spectra of the two anomers of 1-0-acetyl-3,4-di-0-isopropylidene-2,s-anhydro-D, L-allose (2a, 26) are discussed. The reactions of D,L-3,4-di-0-isopropylidene-2,s-anhydroallose (1) with carbethoxymethylenetriphenylphosphorane, bromocarbethoxymethylenetriphenylphosphorane and ethyl triphenylphosphoranylidene pyruvate to give respectively the olefin derivatives 7, 9, and 10 and an internal Michael addition product 11 are described. From 11, two bis-homo anhydro-C-nucleosides having 6-azauracil (15) and 4-hydroxy-5-carboxarnidopyrazole (19) bases were synthesized. GEORGE JUST, MOHABIR RAMJEESINGH, et TENG JIAM LIAK. Can. J. Chem. 54, 2940Chem. 54, (1976. Les spectres rmn des deux anomkres du 0-acktyl-1 di-0-isopropylidene-3,4 anhydro-2,s D,L-allose (2a, 2b) sont rapport& et discutks. On dhrit aussi les rkactions du di-0-isopropylidkne-3,4 anhydro-2,5 D,L-allose avec le carbCthoxymkthylene triphenylphosphoranne, le bromocarbkthoxymkthylene triphCnylphosphoranne et le triphknylphosphorannylidene pyruvate d'kthyle donnant respectivement les dkrivks olkfiniques 7, 9, 10 et le produit de condensation interne de Michael 11. A partir du compose 11, on a synthCtisC deux bis-homo anhydro-CnuclCosides ayant les bases aza-6 uracile 15 et hydroxy-4 carboxamidopyrazole-5 19.In previous papers (l,2), we reported a synthesis of ~,~-3,4-di-O-i~0pr0pylidene-2,5-anhydroallose (1) and its use for C-nucleoside syntheses. In this paper we wish to present a study of the reactions of D,L-3,4-di-0-isopropylidene-2,5-anhydroallose with Wittig reagents and the syntheses of two bis-homo anhydro-C-nucleosides.In our synthesis of D,L-3,4-di-0-isopropylidene-2,5-anhydroallose, both the a and / 3 anomers were obtained in approximately equal amounts. This conclusion was based on their nmr spectral data in which the anomeric protons of both anomers have different chemical shifts. They appeared at 5.08 and 5.21 ppm and their approximate intensity was half a proton each.It was possible to separate the a and / 3 forms of the acetate derivative (2a, 2b) by thin layer chromatography eluting with ether-hexane (1 :2). The two anomers with Rf = 0.45, mp 64.5-65.6"C, and R, = 0.4, mp 140.5-141.5 "C, had virtually identical infrared and mass spectra but different nmr spectra. Structural assignment of the two anomers were based on their nmr data. Generally for sugars, an equatorial anomeric proton produces a signal at lower field by approximately 25 Hz than an axial proton (3). On this basis, the anomer (Rf = 0.45) with the Can. J. Chem. Downloaded from www.nrcresearchpress.com by 52.36.4.81 on 05/12/18For personal use only.

show abstract

A novel procedure for the preparation of 3-substituted 4-hydroxypyrazole-5-carboxylic acids as an approach to pyrazomycin

Cited by 14 publications

References 1 publication

Chemistry of α-Oxoesters: A Powerful Tool for the Synthesis of Heterocycles

Chemistry of α-Oxoesters: A Powerful Tool for the Synthesis of Heterocycles

Reactions of glyoxals with hydrazones: a new route to 4-hydroxypyrazoles

Syntheses of C-nucleosides. IX. Reactions of D,L-3,4-di-O-isopropylidene-2,5-anhydroallose with Wittig reagents. Syntheses of bis-homo anhydro-C-nucleosides.

Contact Info

Product

Resources

About