Ureido Functionalization through Amine-Urea Transamidation under Mild Reaction Conditions

Ureido-functionalized compounds play an indispensable role in important biochemical processes, as well as chemical synthesis and production. Isocyanates, and KOCN in particular, are the preferred reagents for the ureido functionalization of amine-bearing compounds. In this study, we evaluate the potential of urea as a reagent to graft ureido groups onto amines at relatively low temperatures (<100 °C) in aqueous media. Urea is an inexpensive, non-toxic and biocompatible potential alternative to KOCN for ureido functionalization. From as early as 1864, urea was the go-to reagent for polyurea polycondensation, before falling into disuse after the advent of isocyanate chemistry. We systematically re-investigate the advantages and disadvantages of urea for amine transamidation. High ureido-functionalization conversion was obtained for a wide range of substrates, including primary and secondary amines and amino acids. Reaction times are nearly independent of substrate and pH, but excess urea is required for practically feasible reaction rates. Near full conversion of amines into ureido can be achieved within 10 h at 90 °C and within 24 h at 80 °C, and much slower reaction rates were determined at lower temperatures. The importance of the urea/amine ratio and the temperature dependence of the reaction rates indicate that urea decomposition into an isocyanic acid or a carbamate intermediate is the rate-limiting step. The presence of water leads to a modest increase in reaction rates, but the full conversion of amino groups into ureido groups is also possible in the absence of water in neat alcohol, consistent with a reaction mechanism mediated by an isocyanic acid intermediate (where the water assists in the proton transfer). Hence, the reaction with urea avoids the use of toxic isocyanate reagents by in situ generation of the reactive isocyanate intermediate, but the requirement to separate the excess urea from the reaction product remains a major disadvantage.

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The Discovery of Ultrasound Irradiation as a Useful Tool for Accelerating Petasis Three-component Reaction: Synthesis of α-Arylglycines

Current Organic Synthesis ◽

10.2174/1570179414666170821115834 ◽

2018 ◽

Vol 15 (2) ◽

pp. 256-266 ◽

Cited By ~ 2

Author(s):

Fan Yun ◽

Chunhui Cheng ◽

Jingxuan Li ◽

Pingwah Tang ◽

Qipeng Yuan

Keyword(s):

Reaction Time ◽

Glyoxylic Acid ◽

Reaction Times ◽

Ultrasound Irradiation ◽

Secondary Amines ◽

One Pot ◽

Petasis Reaction ◽

Three Component Reaction ◽

Wide Range ◽

High Yields

Aim and Objective: α-Arylglycines belong to an important class of non-proteinogenic amino acids. Petasis 3-component, one-pot reaction lends itself to be suitable for the synthesis of α-Arylglycines. Because of the low reactivity, Petasis reaction requires long reaction time. Our objective is to use ultrasound irradiation to accelerate this versatile Petasis' synthesis of α-Arylglycines. Materials and Methods: Ultrasound irradiation as a physical tool to accelerate the Petasis 3-component reaction without any auxiliary catalyst can significantly shorten the reaction time. The operation is simple. It can be applied to a wide range of substrates. In order to highlight the remarkable utility of the ultrasound in Petasis reaction, we have compared side-by-side the reactivity between the reaction with ultrasound and the one without ultrasound. Results: Using ultrasound, the reaction times of Petasis reactions with various amine substrates including primary and secondary amines, heterocyclic amines, with a wide variety of boronic acids having different substituents (activating and deactivating groups) in the phenyl rings, and with glyoxylic acid and salicylic aldehyde were shortened from 5 to more than 20-fold. Conclusion: We have discovered the first examples of an efficient ultrasound-promoted approach for Petasis reaction to prepare a series of α-arylglycines in high yields and in excellent purities. The low reactivity of the reactions in this study were significantly enhanced by the ultrasound irradiation. By virtue of the acceleration and the operational simplicity, the present ultrasound assisted Petasis reaction can find applications in the synthetic areas of the already widely used Petasis three-component reaction.

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Enhancement of Lipase Enzyme Activity in Non-Aqueous Media through a Rapid Three Phase Partitioning and Microwave Irradiation

E-Journal of Chemistry ◽

10.1155/2008/920408 ◽

2008 ◽

Vol 5 (4) ◽

pp. 864-871 ◽

Cited By ~ 7

Author(s):

N. Saifuddin ◽

A. Z. Raziah

Keyword(s):

Microwave Irradiation ◽

Enzyme Stability ◽

Aqueous Media ◽

Reaction Rates ◽

Initial Reaction ◽

Phase Partitioning ◽

Three Phase ◽

Wide Range ◽

Time Required ◽

Separation Strategy

Three phase partitioning is fast developing as a novel bio-separation strategy with a wide range of applications including enzyme stability and enhancement of its catalytic activity. pH tuning of enzyme is now well known for use in non-aqueous systems. Tuned enzyme was prepared using a rapid drying technique of microwave dehydration (time required around 15 minutes). Further enhancement was achieved by three phase partitioning (TPP) method. With optimal condition of ammonium sulphate andt-butanol, the protein appeared as an interfacial precipitate between uppert-butanol and lower aqueous phases. In this study we report the results on the lipase which has been subjected to pH tuning and TPP, which clearly indicate the remarkable increase in the initial rate of transesterification by 3.8 times. Microwave irradiation was found to increase the initial reaction rates by further 1.6 times, hence giving a combined increase in activity of about 5.4 times. Hence it is shown that microwave irradiation can be used in conjunction with other strategies (like pH tuning and TPP) for enhancing initial reaction rates.

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One-pot and Three-Component Synthesis of α-Benzylamino Pyrones

Journal of Chemical Research ◽

10.3184/174751917x14837116219690 ◽

2017 ◽

Vol 41 (1) ◽

pp. 42-44 ◽

Cited By ~ 1

Author(s):

Jilla Sanchooli ◽

Alireza Hassanabadi

Keyword(s):

Oxalic Acid ◽

Aqueous Media ◽

Reaction Times ◽

Aromatic Aldehydes ◽

Secondary Amines ◽

Reaction Conditions ◽

One Pot ◽

Aerobic Conditions ◽

Salient Features ◽

High Yields

The synthesis of α-benzylamino pyrones is described involving the reaction of 4-hydroxy-6-methyl-2 H-pyran-2-one with aromatic aldehydes and secondary amines in the presence of oxalic acid and in aqueous media. The salient features of this protocol are aerobic conditions, short reaction times, milder reaction conditions without additives and high yields.

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The Management of Post-Tonsillectomy Morbidity in Patients With Sleep Apnoea

Revista de Chimie ◽

10.37358/rc.19.10.3738 ◽

2019 ◽

Vol 70 (10) ◽

pp. 3738-3740

Keyword(s):

Day Surgery ◽

Sleep Apnoea ◽

Integrative Approach ◽

Multicenter Studies ◽

Therapeutic Modalities ◽

Advantages And Disadvantages ◽

Obstructive Sleep ◽

Wide Range ◽

The Impact ◽

Surgery Center

The Tonsillectomy in children or adults is an intervention commonly encountered in the ENT (Ear Nose and Throat) and Head and Neck surgeon practice. The current tendency is to perform this type of surgery in major ambulatory surgery centers. Two objectives are thus pursued: first of all, the increase of the patient quality of life through the reintegration into the family as quickly as possible and secondly, the expenses associated with continuous hospitalization are reduced. Any tertiary (multidisciplinary) sleep center must ensure the complete diagnosis and treatment (including surgery) of sleep respiratory disorders. Under these conditions the selection of patients and especially the implementation of the specific protocols in order to control the postoperative complications it becomes essential. The present paper describes our experience of tonsillectomy as treatment for selected patients with chronic rhonchopathy (snoring) and mild to moderate obstructive sleep apnoea. It was presented the impact of antibiotics protocols in reducing the main morbid outcomes following tonsillectomy, in our day surgery center. The obtained results can also be a prerequisite for the integrative approach of the patients with sleep apnoea who were recommended surgical treatment. Considering the wide range of therapeutic modalities used in sleep apnoea, each with its specific advantages and disadvantages, more extensive and multicenter studies are needed. Keywords: post-tonsillectomy morbidity, day surgery center, sleep disorders

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Advances in Triazole Synthesis from Copper-catalyzed Azide-alkyne Cycloadditions (CuAAC) Based on Eco-friendly Procedures

Current Organic Synthesis ◽

10.2174/1570179416666190104141454 ◽

2019 ◽

Vol 16 (2) ◽

pp. 244-257 ◽

Cited By ~ 2

Author(s):

Marcus Vinicius Nora de Souza ◽

Cristiane França da Costa ◽

Victor Facchinetti ◽

Claudia Regina Brandão Gomes ◽

Paula Mázala Pacheco

Keyword(s):

Biological Activities ◽

Reaction Times ◽

Water Extract ◽

Fish Bone ◽

New Drugs ◽

Bone Powder ◽

Wide Range ◽

Recoverable Catalysts ◽

Egg Shell ◽

Work Up

Background: 1,2,3-triazoles are an important class of organic compounds and because of their aromatic stability, they are not easily reduced, oxidized or hydrolyzed in acidic and basic environments. Moreover, 1,2,3-triazole derivatives are known by their important biological activities and have drawn considerable attention due to their variety of properties. The synthesis of this nucleus, based on the click chemistry concept, through the 1,3-dipolar addition reaction between azides and alkynes is a well-known procedure. This reaction has a wide range of applications, especially on the development of new drugs. Methods: The most prominent eco-friendly methods for the synthesis of triazoles under microwave irradiation published in articles from 2012-2018 were reviewed. Results: In this review, we cover some of the recent eco-friendly CuAAC procedures for the click synthesis of 1,2,3-triazoles with remarks to new and easily recoverable catalysts, such as rhizobial cyclic β-1,2 glucan; WEB (water extract of banana); biosourced cyclosophoraose (CyS); egg shell powder (ESP); cyclodextrin (β- CD); fish bone powder; nanoparticle-based catalyst, among others. Conclusion: These eco-friendly procedures are a useful tool for the synthesis of 1,2,3-triazoles, providing many advantages on the synthesis of this class, such as shorter reaction times, easier work-up and higher yields when compared to classical procedures. Moreover, these methodologies can be applied to the industrial synthesis of drugs and to other areas.

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Advancements in Assessments of Bio-Tissue Engineering and Viable Cell Delivery Matrices Using Bile Acid-Based Pharmacological Biotechnologies

Nanomaterials ◽

10.3390/nano11071861 ◽

2021 ◽

Vol 11 (7) ◽

pp. 1861

Author(s):

Armin Mooranian ◽

Melissa Jones ◽

Corina Mihaela Ionescu ◽

Daniel Walker ◽

Susbin Raj Wagle ◽

...

Keyword(s):

Tissue Engineering ◽

Viable Cell ◽

Cell Delivery ◽

Artificial Organ ◽

Bioartificial Pancreas ◽

Advantages And Disadvantages ◽

Wide Range ◽

Bioartificial Organs ◽

Significant Interest ◽

Modern Technologies

The utilisation of bioartificial organs is of significant interest to many due to their versatility in treating a wide range of disorders. Microencapsulation has a potentially significant role in such organs. In order to utilise microcapsules, accurate characterisation and analysis is required to assess their properties and suitability. Bioartificial organs or transplantable microdevices must also account for immunogenic considerations, which will be discussed in detail. One of the most characterized cases is the investigation into a bioartificial pancreas, including using microencapsulation of islets or other cells, and will be the focus subject of this review. Overall, this review will discuss the traditional and modern technologies which are necessary for the characterisation of properties for transplantable microdevices or organs, summarizing analysis of the microcapsule itself, cells and finally a working organ. Furthermore, immunogenic considerations of such organs are another important aspect which is addressed within this review. The various techniques, methodologies, advantages, and disadvantages will all be discussed. Hence, the purpose of this review is providing an updated examination of all processes for the analysis of a working, biocompatible artificial organ.

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ChCl: Gly (DESs) Promote Environmentally Benign Synthesis of Xanthene Derivatives and Their Antitubercular Activity

Molecules ◽

10.3390/molecules26123667 ◽

2021 ◽

Vol 26 (12) ◽

pp. 3667

Author(s):

Mashooq A. Bhat ◽

Ahmed M. Naglah ◽

Siddique Akber Ansari ◽

Hanaa M. Al-Tuwajiria ◽

Abdullah Al-Dhfyan

Keyword(s):

Reaction Times ◽

Antitubercular Activity ◽

Antimycobacterial Activity ◽

Environmentally Benign ◽

Reaction Yield ◽

Benign Synthesis ◽

Xanthene Derivatives ◽

Wide Range ◽

Major Application

A ChCl: Gly (DESs) promoted environmentally benign method was developed for the first time using the reaction of aryl aldehydes and dimedone to give excellent yields of xanthene analogues. The major application of this present protocol is the use of green solvent, a wide range of substrate, short reaction times, ease of recovery, the recyclability of the catalyst, high reaction yield, and ChCl: Gly as an alternative catalyst and solvent. In addition to this, all the synthesized compounds were evaluated for their in vitro antimycobacterial activity against M. tuberculosis H37Ra (MTB) and M. bovis BCG strains. The compounds 3d, 3e, 3f, and 3j showed significant antitubercular activity against MTB and M. bovis strains with minimum inhibitory concentration (MIC) values of 2.5−15.10 µg/mL and 0.26–14.92 µg/mL, respectively. The compounds 3e, 3f, and 3j were found to be nontoxic against MCF-7, A549, HCT 116, and THP-1 cell lines. All the prepared compounds were confirmed by 1H NMR and 13C NMR analysis.

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Mass and Heat Transfer Coefficients in Automotive Exhaust Catalytic Converter Channels

Catalysts ◽

10.3390/catal9060507 ◽

2019 ◽

Vol 9 (6) ◽

pp. 507

Author(s):

Chrysovalantis C. Templis ◽

Nikos G. Papayannakos

Keyword(s):

Heat Transfer ◽

Flow Reactor ◽

Catalytic Converter ◽

Reaction Rates ◽

Cfd Model ◽

Automotive Exhaust ◽

Transfer Coefficients ◽

Heat Transfer Coefficients ◽

Wide Range ◽

Mass And Heat Transfer

Mass and heat transfer coefficients (MTC and HTC) in automotive exhaust catalytic monolith channels are estimated and correlated for a wide range of gas velocities and prevailing conditions of small up to real size converters. The coefficient estimation is based on a two dimensional computational fluid dynamic (2-D CFD) model developed in Comsol Multiphysics, taking into account catalytic rates of a real catalytic converter. The effect of channel size and reaction rates on mass and heat transfer coefficients and the applicability of the proposed correlations at different conditions are discussed. The correlations proposed predict very satisfactorily the mass and heat transfer coefficients calculated from the 2-D CFD model along the channel length. The use of a one dimensional (1-D) simplified model that couples a plug flow reactor (PFR) with mass transport and heat transport effects using the mass and heat transfer correlations of this study is proved to be appropriate for the simulation of the monolith channel operation.

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Electrolyte-Assisted Hydrogen Cycling in Lithium and Sodium Alanates at Low Pressures and Temperatures

Energies ◽

10.3390/en13225868 ◽

2020 ◽

Vol 13 (22) ◽

pp. 5868

Author(s):

Jason Graetz ◽

John J. Vajo

Keyword(s):

Growth Parameters ◽

Reaction Times ◽

Hydrogen Uptake ◽

Hydrogen Desorption ◽

Reaction Rates ◽

Rate Coefficients ◽

Aluminum Hydrides ◽

Dehydrogenation Reactions ◽

Low Pressures ◽

Sodium Alanates

An investigation of electrolyte-assisted hydrogen storage reactions in complex aluminum hydrides (LiAlH4 and NaAlH4) reveals significantly reduced reaction times for hydrogen desorption and uptake in the presence of an electrolyte. LiAlH4 evolves ~7.8 wt% H2 over ~3 h in the presence of a Li-KBH4 eutectic at 130 °C compared to ~25 h for the same material without the electrolyte. Similarly, NaAlH4 exhibits 4.8 wt% H2 evolution over ~4 h in the presence of a diglyme electrolyte at 150 °C compared to 4.4 wt% in ~15 h for the same material without the electrolyte. These reduced reaction times are composed of two effects, an increase in reaction rates and a change in the reaction kinetics. While typical solid state dehydrogenation reactions exhibit kinetics with rates that continuously decrease with the extent of reaction, we find that the addition of an electrolyte results in rates that are relatively constant over the full desorption window. Fitting the kinetics to an Avrami-Erofe’ev model supports these observations. The desorption rate coefficients increase in the presence of an electrolyte, suggesting an increase in the velocities of the reactant-product interfaces. In addition, including an electrolyte increases the growth parameters, primarily for the second desorption steps, resulting in the observed relatively constant reaction rates. Similar effects occur upon hydrogen uptake in NaH/Al where the presence of an electrolyte enables hydrogenation under more practical low temperature (75 °C) and pressure (50 bar H2) conditions.

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Severe violations of independence in response inhibition tasks

Science Advances ◽

10.1126/sciadv.abf4355 ◽

2021 ◽

Vol 7 (12) ◽

pp. eabf4355

Author(s):

Patrick G. Bissett ◽

Henry M. Jones ◽

Russell A. Poldrack ◽

Gordon D. Logan

Keyword(s):

Response Inhibition ◽

Theoretical Foundation ◽

Reaction Times ◽

Stop Signal ◽

Experimental Paradigm ◽

Signal Delay ◽

Independence Assumption ◽

Analysis Techniques ◽

Wide Range ◽

Saccadic Responses

The stop-signal paradigm, a primary experimental paradigm for understanding cognitive control and response inhibition, rests upon the theoretical foundation of race models, which assume that a go process races independently against a stop process that occurs after a stop-signal delay (SSD). We show that severe violations of this independence assumption at short SSDs occur systematically across a wide range of conditions, including fast and slow reaction times, auditory and visual stop signals, manual and saccadic responses, and especially in selective stopping. We also reanalyze existing data and show that conclusions can change when short SSDs are excluded. Last, we suggest experimental and analysis techniques to address this violation, and propose adjustments to extant models to accommodate this finding.

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