ChemInform Abstract: SYNTHESES BASED ON DIMETHYLPYRAZOLES. II. SYNTHESIS AND TRANSFORMATIONS OF 1,3‐DIMETHYL‐4‐NITRO‐5‐BROMOPYRAZOLE

Andreeva, M. A.; Bolotov, M. I.; Isaev, Sh. G.; Mushii, R. Ya.; Перевалов, В. П.; Seraya, V. I.; Stepanov, B. I.

doi:10.1002/chin.198109229

Cited by 2 publications

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“…We initially investigated the preparation of 3 utilizing a variety of known methodologies for 3-bromopyrazoles, but these approaches were unsuccessful. For example, bromination of 6 is known to lead to bromide 7 ; 6 was resistant to oxidation, and N -methylation of 14 led to a mixture of regioisomers. Likewise, C(3) bromination of 9 led to undesired decarboxylation/bromination to afford 11 , while attempted Hunsdiecker decarboxylation/halogenation of 12 led to bromide 13 (Figure ).…”

Section: Resultsmentioning

confidence: 99%

Development of Scalable Processes for the Preparation of N-Methyl-3-Bromo-5-Methyl Pyrazole

Fox

Markwalter

Zhu

et al. 2017

Org. Process Res. Dev.

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The development and optimization of two scalable routes to N-methyl-3-bromo-5-methyl pyrazole is described. The initial Sandmeyer route entailed a three-step sequence from crotonitrile and methyl hydrazine, proceeding through the 3amino pyrazole intermediate. Due to the GTI liability of the 3-amino pyrazole intermediate, a tedious steam-distillation, and <30% overall yield, we developed a second-generation Sandmeyer-free approach from methyl crotonate and methyl hydrazine which leveraged a condensation, bromination, and oxidation sequence. Process development led to the improved preparation of N-methyl-3-bromo-5-methyl pyrazole with increased efficiency and overall yield. The isolation, handling, and storage of the final product was greatly improved through the generation of the triflic acid salt, and salt form studies are also discussed.

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Section: Resultsmentioning

confidence: 99%

Development of Scalable Processes for the Preparation of N-Methyl-3-Bromo-5-Methyl Pyrazole

Fox

Markwalter

Zhu

et al. 2017

Org. Process Res. Dev.

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“…172 Related reactions were recently reported with many disulfides along with the use of copper. 451 Many nitrogen-bearing 452 (including ammonia 63 ) or oxygen-bearing 77,453 nucleophiles as well as cyanides 454 were also used. 312 On the other hand, copper and a high temperature were necessary for substitution of 3-bromo-1-methyl-4-nitropyrazole by ammonium hydroxide.…”

Section: Chemistry Of 4-halogenoyrazolesmentioning

confidence: 99%

Preparation and Chemistry of 3/5-Halogenopyrazoles

Janin

2012

Chem. Rev.

173

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3924 2. Electrophilic Halogenations 3925 2.1. Electrophilic Halogenation of Pyrazoles 3925 2.2. Halogenation of Pyrazole Anions 3929 3. Preparations from 3/5-Hydroxy-or 3/5-Aminopyrazoles 3930 3.1. Dehydroxyhalogenation of 3/5-Hydroxypyrazoles 3930 3.2. Halogenodediazoniation of 3/5-Aminopyrazoles 3934 4. Rearrangements, Cycloadditions, and Condensations 3936 4.1. Rearrangement of Pyrazole N-Oxides 3936 4.2. Cycloadditions 3937 4.3. Condensations 3938 5. Modifications of 3/5-Halogenopyrazoles 3940 6. Miscellaneous 3943 7. Chemistry of Halogenopyrazoles 3944 7.1. Chemistry of 4-Halogenoyrazoles 3944 7.1. Chemistry of 3/5-Halopyrazoles and Activated Esters of Hydroxypyrazoles 3947 7.3. CH Activation of Pyrazoles 3949 8. Conclusion 3951 Author Information 3951 Corresponding Author 3951 Notes 3951 Biography 3951 Acknowledgments 3951 References 3951

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ChemInform Abstract: SYNTHESES BASED ON DIMETHYLPYRAZOLES. II. SYNTHESIS AND TRANSFORMATIONS OF 1,3‐DIMETHYL‐4‐NITRO‐5‐BROMOPYRAZOLE

Abstract: 1,3‐Dimethylpyrazol (I) läßt sich stufenweise bromieren, wobei die Derivate (II) bzw. (III) entstehen.

Cited by 2 publications

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Development of Scalable Processes for the Preparation of N-Methyl-3-Bromo-5-Methyl Pyrazole

Development of Scalable Processes for the Preparation of N-Methyl-3-Bromo-5-Methyl Pyrazole

Preparation and Chemistry of 3/5-Halogenopyrazoles

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