scholarly journals A two-phase bromination process using tetraalkylammonium hydroxide for the practical synthesis of α-bromolactones from lactones

2021 ◽  
Vol 17 ◽  
pp. 2906-2914
Author(s):  
Yuki Yamamoto ◽  
Akihiro Tabuchi ◽  
Kazumi Hosono ◽  
Takanori Ochi ◽  
Kento Yamazaki ◽  
...  

A simple and efficient method for α-brominating lactones that affords α-bromolactones under mild conditions using tetraalkylammonium hydroxide (R4N+OH−) as a base was developed. Lactones are ring-opened with Br2 and a substoichiometric amount of PBr3, leading to good yields of the corresponding α-bromocarboxylic acids. Subsequent intramolecular cyclization over 1 h using a two-phase system (H2O/CHCl3) containing R4N+OH− afforded α-bromo lactones in good yields. This method can be applied at the 10 mmol scale using simple operations. α-Bromo-δ-valerolactone, which is extremely reactive and difficult to isolate, could be isolated and stored in a freezer for about one week using the developed method. Optimizing the solvent for environmentally friendly large-scale syntheses revealed that methyl ethyl ketone (MEK) was as effective. In addition, in situ-generated α-bromo-δ-valerolactone was directly converted into a sulfur-substituted functional lactone without difficulty by reacting it with a sulfur nucleophile in one pot without isolation. This new bromination system is expected to facilitate the industrial use of α-bromolactones as important intermediates.

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chuhan Li ◽  
Shuo Song ◽  
Yuling Li ◽  
Chang Xu ◽  
Qiquan Luo ◽  
...  

AbstractHomogeneous earth-abundant metal catalysis based on well-defined molecular complexes has achieved great advance in synthetic methodologies. However, sophisticated ligand, hazardous activator and multistep synthesis starting from base metal salts are generally required for the generation of active molecular catalysts, which may hinder their broad application in large scale organic synthesis. Therefore, the development of metal cluster catalysts formed in situ from simple earth-abundant metal salts is of importance for the practical utilization of base metal resource, yet it is still in its infancy. Herein, a mixture of catalytic amounts of cobalt (II) iodide and potassium tert-butoxide is discovered to be highly active for selective hydroboration of vinylarenes and dihydroboration of nitriles, affording a good yield of diversified hydroboration products that without isolation can readily undergo further one pot transformations. It should be highlighted that the alkoxide-pinacolborane combination acts as an efficient activation strategy to activate cobalt (II) iodide for the generation of metastable heterotopic cobalt catalysts in situ, which is proposed to be catalytically active species.


2017 ◽  
Vol 4 (8) ◽  
pp. 1636-1639 ◽  
Author(s):  
Bin Cheng ◽  
Bian Bao ◽  
Yanhe Chen ◽  
Ning Wang ◽  
Yun Li ◽  
...  

A new route to arylhydrazides involving the reaction of two highly active intermediates, the 1,3-zwitterion generated in situ from the Mitsunobu reagent and arynes, under mild conditions has been developed.


2017 ◽  
Vol 13 ◽  
pp. 2023-2027 ◽  
Author(s):  
Hao Wang ◽  
Cui Chen ◽  
Weibing Liu ◽  
Zhibo Zhu

We developed a direct vicinal difunctionalization of alkenes with iodine and TBHP at room temperature. This iodination and peroxidation in a one-pot synthesis produces 1-(tert-butylperoxy)-2-iodoethanes, which are inaccessible through conventional synthetic methods. This method generates multiple radical intermediates in situ and has excellent regioselectivity, a broad substrate scope and mild conditions. The iodine and peroxide groups of 1-(tert-butylperoxy)-2-iodoethanes have several potential applications and allow further chemical modifications, enabling the preparation of synthetically valuable molecules.


2019 ◽  
Vol 136 ◽  
pp. 06025
Author(s):  
Haishan SHI ◽  
Ying YANG ◽  
Weihua LI ◽  
Hui ZHANG ◽  
Xiaolei CHENG

As an indispensable intermediate, androstenedione is widely used in drug manufacturing, especially steroidal drugs. However, the chemical manufacturing process of androstenedione is generally complicated and difficult, and it will cause serious environmental pollution in the production process. The biological method for the production of androstenedione has a very promising development prospect, because it is more economical and environmentally friendly than chemical methods. In order to better produce androstenedione on a large scale, the imbalance between supply and demand can be solved. In this study, the biaqueous phase system was used to increase the substrate concentration, and the method of transforming plant sterol by mycobacterium was used to produce androstenedione. The optimal conditions for the production of androstenedione by microbial assay were determined by orthogonal test: the aqueous two-phase system was water/ sunflower oil, the temperature was 30 °C, the initial pH was 6.5, the substrate concentration was 0.4 g/L, the rotation speed was 250 rpm, and the inoculation was carried out. The amount was 14.83%, the organic ratio was 20.65%, and the liquid loading was 150/500 mL. The preliminary production of androstenedione by microbial method has found suitable process conditions and provided data and theoretical support for its large-scale production.


2021 ◽  
Author(s):  
Byeong-Ui Moon ◽  
Dae Kun Hwang ◽  
Scott S. H. Tsai

We demonstrate the dynamic control of aqueous two phase system (ATPS) droplets in shrinking, growing, and dissolving conditions. The ATPS droplets are formed passively in a flow focusing microfluidic channel, where the dextran-rich (DEX) and polyethylene glycol-rich (PEG) solutions are introduced as disperse and continuous phases, respectively. To vary the ATPS equilibrium condition, we infuse into a secondary inlet the PEG phase from a different polymer concentration ATPS. We find that the resulting alteration of the continuous PEG phase can cause droplets to shrink or grow by approximately 45 and 30 %, respectively. This volume change is due to water exchange between the disperse DEX and continuous PEG phases, as the system tends towards new equilibria. We also develop a simple model, based on the ATPS binodal curve and tie lines, that predicts the amount of droplet shrinkage or growth, based on the change in the continuous phase PEG concentration. We observe a good agreement between our experimental results and the model. Additionally, we find that, when the continuous phase PEG concentration is reduced such that PEG and DEX phases no longer phase separate, the ATPS droplets are dissolved into the continuous phase. We apply this method to controllably release encapsulated microparticles and cells, and we find that their release occurs within 10 seconds. Our approach uses the dynamic equilibrium of ATPS to control droplet size along the microfluidic channel. By modulating the ATPS equilibrium, we are able to shrink, grow, and dissolve ATPS droplets in situ. We anticipate that this approach may find utility in many biomedical settings, for example, in drug and cell delivery and release applications.


2016 ◽  
Author(s):  
Bartłomiej Furman

Amides represent an important class of compounds in chemistry, chemical biology and pharmaceutical industry. Their broad utility in many fields is closely tied to the structure of the amide moiety which endows these compounds with unique features. The low reactivity of amide carbonyls towards nucleophiles is a major obstacle to their further functionalization. Selective activation of amides and lactams enables access to novel reactivity pathways and opens up intriguing perspectives in synthesis. Recently, we have demonstrated that upon treatment with Cp2Zr(H)Cl (Schwartz’s reagent), five- and six-membered lactams, including sugar- and hydroxy acid-derived lactams, can be easily converted into imines under mild conditions. In addition, as was also shown, in situ generated cyclic imines can be directly subjected to further reactions with nucleophilic reagents such as allyltributylstannane, Grignard reagents, enolates or Danishefsky’s diene to afford α-functionalized pyrrolidines, piperidines and polyhydroxylated pyrrolidine peptidomimetic scaffolds in a one-pot manner. The key advantage of the presented approach is the simplicity and convenience of generation of sugar-derived imines from readily available starting materials: sugar-derived lactams. The use of sugar-derived lactams as cyclic imine precursors is crucial to the efficiency of the described synthetic method. These compounds are more readily prepared, handled, and stored than the alternative precursors of cyclic imines such as nitrones, N-chloroamines or azido aldehydes. In the second part of the lecture a method for preparing 2,3-disubstituted indoles from commercially available isatins will be briefly presented.


Synthesis ◽  
2019 ◽  
Vol 51 (22) ◽  
pp. 4170-4182 ◽  
Author(s):  
Lin-Lin Zhang ◽  
Ya-Ting Li ◽  
Ting Gao ◽  
Sha-Sha Guo ◽  
Bei Yang ◽  
...  

A sequential multistep reaction toward 5-thio- or 5-selenotriazoles has been established by generation of both copper(I) triazolides and sulfenylating or selenylating agents in situ, starting from elemental sulfur or selenium. This reaction features mild conditions, readily available and broad-scope substrates, good functional group compatibility, high efficiency and regioselectivity, easy operation, and ligand-free CuI.


Synlett ◽  
2019 ◽  
Vol 30 (20) ◽  
pp. 2290-2294
Author(s):  
Mohammad Ali Nasseri ◽  
Seyyedeh Ameneh Alavi ◽  
Boshra Mahmoudi ◽  
Milad Kazemnejadi

In this study, cyanations or azidations of imines were performed by using hydroxy(dimethyl)-λ4-sulfanecarbonitrile or azido(dimethyl)-λ4-sulfanol, respectively, prepared in situ by treatment of potassium cyanide or sodium azide with a dimethyl sulfoxide–nitric acid combination. Furthermore, a one-pot preparation of 5-substituted 1H-tetrazole derivatives was carried out by using this reagent combination in the presence of an aldehyde, hydroxylamine hydrochloride, and sodium azide under mild conditions.


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