Pyrazole Chemistry in Crop Protection

Lamberth, Clemens

doi:10.3987/rev-07-613

Cited by 250 publications

(101 citation statements)

References 75 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…A series of N-arylsydnones 2 were thus prepared and reacted with equimolar amounts of 1 at 165°C in anisole ( Table 1). As expected the reactions gave rise to mixtures of regioisomeric pyrazolyl boronates 3/4 easily separated by silica gel chromatography, with the pyrazole-3-boronate predominating by a factor of 7:3 as determined by 1 H NMR analysis of the crude mixture of 3 and 4. These results also showed that sydnones bearing electron-poor aryl groups at N-1 gave the best result.…”

mentioning

confidence: 97%

See 1 more Smart Citation

Sequential Suzuki–Miyaura Cross-coupling Reactions of 4-Halopyrazolyl MIDA 3-Boronates: A Modular Synthetic Entry to 3,4-Bis(hetero)aromatic Pyrazoles

DelaunayThierry¹,

Es-SayedMazen²,

VorsJean-Pierre³

et al. 2011

Chemistry Letters

View full text Add to dashboard Cite

The 1,3-dipolar cycloaddition of N-arylsydnones with ethynyl MIDA boronate produces mixtures of the corresponding regioisomeric pyrazolyl 3(4)-boronates, with the pyrazolyl 3-boronates predominating by a factor of 7:3. Further C-4 iodination of the latter opened access to 4-iodopyrazolyl MIDA 3-boronates as valuable scaffolds for the elaboration of unsymmetrically 1,3,4-trisubstituted pyrazole derivatives via Suzuki cross-coupling reactions.Pyrazole derivatives have found numerous applications as pharmaceuticals and agrochemicals.1 As a part of our ongoing research program devoted to the synthesis of diverse poly-(hetero)aromatic pyrazoles for biological screening, we needed an efficient and modular synthetic strategy to assemble a series of 3,4-bis(hetero)aromatic derivatives.2 To this end, flexible protocols allowing the sequential introduction of (hetero)aryl substituents on the prefunctionalized pyrazole nucleus via transition-metal-catalyzed site-selective CC bond forming processes were highly desirable.3 Notably, the Suzuki-type reactions were particularly attractive as they are largely unaffected by the presence of water and are tolerant to a wide range of functional groups. They also take advantage of the commercial availability of numerous boronic acids. 4 However, one major drawback of this strategy is the poor synthetic accessibility of 3,4-dihalogenated pyrazoles. Indeed, while C-4 halogenation of the pyrazole nucleus is relatively easy, 5 selective halogenation at the C-3 carbon atom adjacent to nitrogen remains a rather difficult task. 3,6 In addition, issues of crosscoupling site-selectivity would also need to be addressed.Within this context, we became interested in the potential synthetic utility of 4-halopyrazole-3-boronates as alternative scaffolds. Our approach is inspired by Harrity's pioneering work 2a,7 on the synthesis of pyrazolyl pinacol boronates via sydnone 1,3-dipolar cycloadditions with alkynylboronates. Interestingly, it was reported that terminal alkynylboronate cycloaddition provided the corresponding pyrazole-3-boronates with good levels of regiocontrol, whereas substituted alkynes afforded almost exclusively 4-boronates. Based on these results, we envisaged a rapid access to 4-halopyrazole-3-boronates via sydnone cycloaddition with a terminal alkynyl boronate ester followed by C-4 halogenation. Besides, in order to avoid self coupling reactions, it was decided to make use of masked boronic acids 8 that would allow us to first cross-couple at C-4 and then release the boronic acid to finally cross-couple at C-3. The commercially available ethynyl N-methyliminodiacetic acid (MIDA) boronate (1) developped by Burke 9 was the perfect candidate to gauge the present strategy (Scheme 1). We report herein our preliminary results toward this goal.Our studies began with an initial investigation of the efficiency of sydnone cycloadditions with ethynyl MIDA boronate (1). A series of N-arylsydnones 2 were thus prepared and reacted with equimolar amounts of 1 at 165°C in anisole ( Table 1). As...

show abstract

mentioning

confidence: 97%

“…Our studies began with an initial investigation of the efficiency of sydnone cycloadditions with ethynyl MIDA boronate (1). A series of N-arylsydnones 2 were thus prepared and reacted with equimolar amounts of 1 at 165°C in anisole ( Table 1).…”

mentioning

confidence: 99%

Sequential Suzuki–Miyaura Cross-coupling Reactions of 4-Halopyrazolyl MIDA 3-Boronates: A Modular Synthetic Entry to 3,4-Bis(hetero)aromatic Pyrazoles

DelaunayThierry¹,

Es-SayedMazen²,

VorsJean-Pierre³

et al. 2011

Chemistry Letters

View full text Add to dashboard Cite

show abstract

“…Pyrazole derivatives have broad applications in medicinal [3,4] and agricultural chemistry [5,6]. The pharmacological activity of these compounds is very diverse.…”

Section: Commentmentioning

confidence: 99%

The crystal structure of ethyl 1-(4-nitrophenyl)-5-(trifluoromethyl)-1H-pyrazole-4-carboxylate, C₁₃H₁₀F₃N₃O₄

Jaćimović

Kosović

Bogdanović

et al. 2017

Zeitschrift Für Kristallographie - New Crystal Structures

View full text Add to dashboard Cite

show abstract

“…The pyrazole motif is an important fragment in the pharmaceutical industry and is present in a number of commercial medicines and agrichemicals. 29,30 However, synthetic routes to these structurally important diazoles are often linear or suffer from regioselectivity issues during the heterocycle forming step. In this regard, we felt that sydnones could represent convenient and potentially versatile starting materials to access these desirable therapeutic analogs.…”

Section: Figure 1 Tubulin-binding Vdasmentioning

confidence: 99%

Sydnone Cycloaddition Route to Pyrazole-Based Analogs of Combretastatin A4

et al. 2016

View full text Add to dashboard Cite

The combretastatins are an important class of tubulin-binding agents. Of this family, a number of compounds are potent tumor Vascular Disrupting Agents (VDAs) and have shown promise in the clinic for cancer therapy. We have developed a modular synthetic route to combretastatin analogs based on a pyrazole core through highly-regioselective alkyne cycloaddition reactions of sydnones. These compounds show modest to high potency against human umbilical vein endothelial cell proliferation. Moreover, evidence is presented that these novel VDAs have the same mode of action as CA4P and bind reversibly to -tubulinbelieved to be a key feature in avoiding toxicity. The most active compound from in vitro studies was taken forward to an in vivo model and instigated an increase in tumor cell necrosis.

show abstract

Pyrazole Chemistry in Crop Protection

Cited by 250 publications

References 75 publications

Sequential Suzuki–Miyaura Cross-coupling Reactions of 4-Halopyrazolyl MIDA 3-Boronates: A Modular Synthetic Entry to 3,4-Bis(hetero)aromatic Pyrazoles

Sequential Suzuki–Miyaura Cross-coupling Reactions of 4-Halopyrazolyl MIDA 3-Boronates: A Modular Synthetic Entry to 3,4-Bis(hetero)aromatic Pyrazoles

The crystal structure of ethyl 1-(4-nitrophenyl)-5-(trifluoromethyl)-1H-pyrazole-4-carboxylate, C₁₃H₁₀F₃N₃O₄

Sydnone Cycloaddition Route to Pyrazole-Based Analogs of Combretastatin A4

Contact Info

Product

Resources

About

Pyrazole Chemistry in Crop Protection

Cited by 250 publications

References 75 publications

Sequential Suzuki–Miyaura Cross-coupling Reactions of 4-Halopyrazolyl MIDA 3-Boronates: A Modular Synthetic Entry to 3,4-Bis(hetero)aromatic Pyrazoles

Sequential Suzuki–Miyaura Cross-coupling Reactions of 4-Halopyrazolyl MIDA 3-Boronates: A Modular Synthetic Entry to 3,4-Bis(hetero)aromatic Pyrazoles

The crystal structure of ethyl 1-(4-nitrophenyl)-5-(trifluoromethyl)-1H-pyrazole-4-carboxylate, C13H10F3N3O4

Sydnone Cycloaddition Route to Pyrazole-Based Analogs of Combretastatin A4

Contact Info

Product

Resources

About

The crystal structure of ethyl 1-(4-nitrophenyl)-5-(trifluoromethyl)-1H-pyrazole-4-carboxylate, C₁₃H₁₀F₃N₃O₄