- Method for preparing benzyl carbazate
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The invention provides a method for preparing benzyl carbazate. The method comprises the following steps: (1) adding a dichloromethane solvent and hydrazine hydrate into a reaction kettle, stirring until the dichloromethane solvent and hydrazine hydrate are dissolved, adding a catalyst, and stirring for at least 5 minutes; (2) slowly dropwise adding benzyl chloroformate into the reaction kettle, and carrying out heat preservation reaction for 2 hours; (3) carrying out heat preservation and water separation on the obtained reaction liquid through a liquid separation device, and recycling hydrazine hydrate after water separation; (4) adding hydrochloric acid into an organic phase obtained after water separation, and carrying out acidification refining; (5) adding a sodium carbonate aqueous solution into the acidified and refined solution for neutralization, carrying out cooling crystallization on the neutralized solution, centrifuging, separating the filtrate to remove water, recycling the organic phase, and collecting the crystallized solid for later use; and (6) recrystallizing the collected crystal solid with water to obtain benzyl carbazate. The benzyl carbazate with higher purity is obtained by adding a cooling crystallization method, and the cooling crystallization method is simple, easy to operate and safer for operators.
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Paragraph 0018-0026
(2021/09/04)
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- Method for synthesizing benzyl hydrazinecarboxylate
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The invention relates to the technical field of compound synthesis, in particular to a method for synthesizing benzyl hydrazinecarboxylate. The method comprises the following steps of dissolving hydrazine hydrate in a solvent, adding a catalyst, mixing and stirring the mixture for at least 5 minutes, and introducing inert gas to discharge air; dropwise adding benzyl chloroformate into a reaction vessel in step 1 for a constant-temperature reaction at 20-30 DEG C for at least 2 hours, then raising the temperature for a reaction for at least 30 minutes, lowering the temperature to 80 DEG C or below, then conducting standing for at least 30 minutes, carrying out filtering, combining a filtrate with a washing solution, and conducting distilling under reduced pressure to remove the solvent; adding residues obtained after reduced-pressure distillation into purified water, performing ultrasonic treatment for at least 5 minutes, conducting separation, removing a supernatant, adding methanol for dissolving, and volatilizing methanol until methanol is completely evaporated to obtain pure benzyl hydrazinecarboxylate. According to the method, the problems that the yield of existing benzyl hydrazinecarboxylate is low and the product is not easy to purify in the prior art are solved; prepared benzyl hydrazinecarboxylate has the advantages of high yield, high purity and high material utilization rate.
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Paragraph 0016; 0034-0065
(2019/05/04)
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- Synthesis and application of a novel asymmetric azo reagent: 1-(tert-butyl)-2-(4-chlorobenzyl) azodicarboxylate (tBCAD)
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A series of novel asymmetric azo reagents, 1-(tert-butyl)-2-(4-substituted benzyl) azodicarboxylate, were prepared. The synthetic process has the advantage of simpleness, easy operation, mild reaction condition and high yield. The 1-(tert-butyl)-2-(4-chlorobenzyl) azodicarboxylate (tBCAD) was selected for its stability and convenience to handle, and its precursor can be recycled by recrystallization with toluene. The tBCAD and DIAD were applied to a wide variety of Mitsunobu reactions. The experimental results showed that the performance of tBCAD in Mitsunobu reaction was comparable to that of DIAD, while the stability of tBCAD was much better than DIAD. Thus, tBCAD can be a novel, stable, effective azo-reagent for the Mitsunobu reaction.
- Xie, Jian,Xu, Cai,Dai, Qianjin,Wang, Xiaozhong,Xu, Gang,Chen, Yingqi,Dai, Liyan
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p. 5321 - 5326
(2017/08/04)
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- Gold-catalyzed three-component spirocyclization: A one-pot approach to functionalized pyrazolidines
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An efficient, highly atom economic synthesis of hitherto unknown spirocyclic pyrazolidines in a one-pot process was developed. The gold-catalyzed three-component coupling of alkynols, hydrazines and aldehydes or ketones likely proceeds via cycloisomerization of the alkynol to an exocyclic enol ether and subsequent [3 + 2]-cycloaddition of an azomethine ylide. A library of 29 derivatives with a wide range of functional groups was synthesized in up to 97% yield. With this new method, every position in the final product can be substituted which renders the method ideal for applications in combinatorial or medicinal chemistry.
- Wagner, Bernd,Hiller, Wolf,Ohno, Hiroaki,Krause, Norbert
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supporting information
p. 1579 - 1583
(2016/02/10)
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- Hydrazine carboxylic acid benzyl ester synthesis method
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The invention relates to a synthetic method of benzyl carbazate. The method comprises the following steps of: a), dissolving hydrazine hydrate in a solvent and adding an alkali; b), controlling the reaction temperature to be 20-80 DEG C, dropping benzyl chloroformate; c), removing impurities after salt forming reaction of an obtained crude product; and d), performing basic dissociation of an obtained salt to obtain a pure f benzyl carbazate product. The synthetic method has the advantages of simple operation, good safety, high yield and low production cost, so as to meet a large demand of volume production of new pesticide indoxacarb and other fine chemical products on the key intermediate-benzyl carbazate.
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Paragraph 0024-0027
(2017/04/25)
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- Platinum-catalyzed intramolecular hydrohydrazination: Evidence for alkene insertion into a Pt-n bond
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Dicationic (bpy)Pt(II) complexes were found to catalyze the intramolecular hydrohydrazination of alkenes. Reaction optimization revealed Pt(bpy)Cl 2 (10 mol %) and AgOTf (20 mol %) in DMF-d7 to be an effective catalyst system for the conversion of substituted hydrazides to five- and six-membered N-amino lactams (N-amino = N-acetamido at 120 A°C, N-phthalimido at 80 A°C, -OTf = trifluoromethanesulfonate). Of the four possible regioisomeric products, only the product of 5-exo cyclization at the proximal nitrogen is formed, without reaction at the distal nitrogen or 6-endo cyclization. The resting states were found to be a 2:1 Pt-amidate complex (25, for N-acetamido) of the deprotonated hydrazide and a Pt-alkyl complex of the cyclized pyrrolidinone (20 for N-phthalimido). Both complexes are catalytically competent. Catalysis using 25 as the precatalyst shows no rate dependence on added acid (HOTf) or base (2,6-lutidine). The available mechanistic data are all consistent with a mechanism involving N-H activation of the hydrazide, followed by insertion of the alkene into the Pt-N bond, and finally protonation of the resulting cyclized alkyl complex by hydrazide to release the hydrohydrazination product and regenerate the active Pt-amidate catalyst.
- Hoover, Jessica M.,Dipasquale, Antonio,Mayer, James M.,Michael, Forrest E.
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supporting information; experimental part
p. 5043 - 5053
(2010/06/13)
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- Synthesis of pyrazolo[5,1-d][1,2,3,5]tetrazine-4(3H)-ones
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A solid-phase synthesis of 5-aminopyrazole has been developed and applied to the preparation of pyrazolo[5,1-d]-[1,2,3,5]tetrazine-4(3H)-ones. In this strategy, a one-pot reaction from 5-aminopyrazoles to the pyrazolo[5,1-d]-[1,2, 3,5]tetrazine-4(3H)-ones which provided the compounds in good yields was demonstrated. Using this synthetic strategy, we prepared a representative set of 16 pyrazolo[5,1-d][l,2,3,5]tetrazine-4(3H)-ones.
- Gao, Yaojun,Lam, Yulin
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experimental part
p. 69 - 74
(2010/10/04)
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- A selective method for cleavage of N-Troc-protected hydrazines and amines under mild conditions using mischmetal and TMSCI
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The Troc (2,2,2-trichloroethoxycarbonyl) protecting group was efficiently removed under neutral conditions from corresponding protected hydrazines and amines using mischmetal in good to excellent yields. Two new substituted hydrazines were synthesised.
- Vellemaee, Eerold,Lebedev, Oleg,Sillard, Rannar,Maeeorg, Uno
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p. 685 - 687
(2007/10/03)
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- Benzyloxy(4-substituted benzyloxy)carbenes. Generation from oxadiazolines and fragmentation to radical pairs in solution
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Thermolysis of 2,2-dibenzyloxy-5,5-dimethyl-Δ3-1,3,4-oxadiazoline in benzene at 110°C leads to dibenzyloxycarbene. The carbene was trapped with tert-butyl alcohol to afford dibenzyl-tert-butyl orthoformate. In the absence of a trapping agent for the carbene, it fragmented to benzyloxycarbonyl and benzyl radicals, as shown by trapping the latter with TEMPO. In the absence of both TEMPO and tert-butyl alcohol, the radicals were partitioned between coupling to benzyl phenylacetate and decarboxylation, with subsequent formation of bibenzyl. The preferred sense of fragmentation of the analogous carbenes from benzyloxy-(p-substituted-benzyloxy)carbenes was determined by comparing the yields of the two possible esters, ArCH2O(CO)CH2Ph and PhCH2O(CO)CH2Ar. It was found that an electron-withdrawing group in the para position favoured fragmentation to the benzylic radical containing that group. A Hammett plot of the data gave a best fit with σ- substituent constants (r = 0.994, ρ((PhH, 110°C) = 0.7)) suggesting that the fragmentation involves charge separation in the sense that increases electron density on the group that is becoming a benzylic radical and decreases electron density on the carbonyl group that is becoming the benzyloxycarbonyl radical.
- Merkley,Warkentin
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p. 942 - 949
(2007/10/03)
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- Flavin chemical models for monoamine oxidase inactivation by cyclopropylamines, α-silylamines, and hydrazines
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Models for the inactivation of the monoamine oxidase A and B, two closely related flavoenzymes, by cyclopropylamines, α-silylamines, and hydrazines have been investigated in order to gain insight into the possible chemical mechanisms for these processes. The activated (i.e. high reduction potential and electrophilicity) flavin, 3-methyl-5-ethyllumiflavinium perchlorate (5), was employed in this effort along with trans-2-phenylcyclopropylamine (1), a host of monosubstituted hydrazines (13-16), and α-(trimethylsilyl)benzylamine (9). Admixture of 5 with 1 (25°C, MeCN) results in instantaneous formation of the stable and completely characterized flavin-amine adducts 6 (K(e) = 2 x 104) derived by addition of the amine function in 1 to the 4a-position of 5. Reaction of the 4a-adduct 6 with cyclopropylamine 1 (85°C, MeCN) cleanly (80%) produces the aldimine 7 formed by condensation of the initial product, trans-cinnamaldehyde and amine 5. These results demonstrate that 4a-adducts related to 6 are capable of undergoing cyclopropane ring opening reactions by polar pathways to produce electrophilic α,β-unsaturated carbonyl products. Consequently, ring opening reactions proposed for monoamne oxidase inactivation by primary and perhaps secondary cyclopropylamines can occur by polar routes and, thus, are not uniquely attributable to radical mechanistic pathways. In a similar manner, the flavinium salt 5 undergoes rapid reaction with the α-silylamine 9 to produce a stable 4a-adduct 10 (K(e) = 7 x 104). Reaction of this adduct with 9 (45°C, MeCN) leads to initial production of N-[(α-trimethylsilyl)benzyl]benzaldimine (12) which undergoes desilylation to produce N-benzylbenzaldimine (11) under these conditions. Also, 4a-adduct 10 is rapidly converted to aldilne 11 by reaction with TBAF at 25°C in MeCN. These results show that 4a-adducts, generated from activated flavins and α-silylamines, participate in fragmentation processes leading to silylation of nucleophiles and production of carbonyl products. This polar mechanistic pathway models the known inactivation reactions of the MAOs by α-silylamines previously attributed to SET (radical) routes. Reaction of flavinium salt 5 with phenyl- or benzylhydrazine results in formation of 4a-phenyl or -benzyl flavin adducts. For example, admixture of 5 and PhNHNH2 in CH3CN at 25°C provides the characterizable 4a-phenyl and 4a-cyanomethyl flavins, 21 (28%) and 22 (55%), and benzene. Benzylhydrazine reacts similarly with 5 to produce only the 4a-benzyl adduct 23 (89%). Information about the mechanism for adduct formation in these reactions has come from studies with the hydrazine analogs, NH2NHCO2CH2Ph (15) and NH2OCH2Ph (16). These substances react rapidly with 5 in MeCN at 25°C to cleanly produce stable 4a-hydrazine adducts, 17. The results suggest that 4a-alkylation or -arylation reactions of the activated flavin 5 with hydrazines probably occur via the intermediacy of 4a-hydrazine flavin adducts related to 17. Thus, a polar mechanistic model is also consistent with the known inactivation reactions of the MAOs with hydrazines which are also reported to generate 4a-flavin alkylated and arylated MAO derivatives.
- Kim, Jong-Man,Hoegy, Susan E.,Mariano, Patrick S.
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p. 100 - 105
(2007/10/02)
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