scholarly journals Supercritical Carbon Dioxide Effect on Lipase-Catalyzed Geranyl Acetate Synthesis

Author(s):  
Matheus Tavares ◽  
Luís Kanda ◽  
Wanderson Giacomin Júnior ◽  
Luiz Ramos ◽  
Luciana Vandenberghe ◽  
...  

This work provides a general insight on lipase-catalyzed synthesis of geranyl acetate through esterification of geraniol with acetic acid. Although this reaction is relatively well known, the replacement of organic solvents by supercritical fluids is fairly recent and the role of CO2 is still not completely understood. Therefore, reactions were performed with Lipozyme® RM IM and Novozym® 435 as biocatalysts, and hexane and CO2 as solvents. For similar reaction conditions, geraniol conversions obtained using hexane were much higher, rather than supercritical CO2 (scCO2, 82.9% versus 12.0% after 4 h). The results obtained indicated that CO2 might help the migration of water from the enzyme surface to reaction bulk and then to the vapor phase. Thus, by increasing the vapor phase extension, the geraniol conversion enhanced to 60.5% after 4 h. Such improvement represents one step forward to comprehend the influence of CO2, a safer and greener solvent as compared to hexane.

Synlett ◽  
2021 ◽  
Author(s):  
Kripa Subramanian ◽  
Subhash L. Yedage ◽  
Kashish Sethi ◽  
Bhalchandra M. Bhanage

An electrochemical method for the synthesis of phenanthridinones via constant potential electrolysis (CPE) mediated by <i>n</i>-Bu<sub>4</sub>NI (TBAI) has been reported. The protocol is metal and oxidant free and proceeds with 100% current efficiency. Here TBAI plays the dual role of the redox catalyst as well as supporting electrolyte. The intramolecular C-H activation proceeds under mild reaction conditions and short reaction time via electrochemically generated amidyl radicals. The reaction has been scaled up to gram level showing its practicability and the synthetic utility and applicability of the protocol has been demonstrated by the direct one-step synthesis of the bioactive compound Phenaglaydon.


2019 ◽  
Vol 16 (2) ◽  
pp. 276-282 ◽  
Author(s):  
Yu Liu ◽  
Duodong Zhang ◽  
Yangyang Ma ◽  
Jiayun Li ◽  
Ying Bai ◽  
...  

Aim and Objective: The hydrosilylation reaction of carbonyl compounds has emerged as a powerful method in organic synthesis. The catalytic hydrosilylation of ketones is a valuable transformation because it generates protected cyanosilylation reaction of carbonyl compounds is an efficient procedure for the synthesis of silylated cyanohydrins, which are readily converted into useful functionalized compounds, such as cyanohydrins, α-hydroxy acids, β-amino alcohols and other biologically active compounds. Materials and Methods: A facile, economic and efficient method has been developed for the hydrosilylation and cyanosilylation of ketones using metal borohydrides. A series of silylated ethers and silylated cyanohydrins can be isolated via direct distillation. Results: The catalytic properties of a range of metal borohydrides in the hydrosilylation reaction of acetophenone with diphenylsilane were investigated. The relative catalytic activity of the borohydride catalyst studied was as follows: (CH3)4NBH4> (PhCH2)(CH3)3NBH4> (CH2CH3)4NBH4> (CH3CH2CH2CH3)4NBH4> NaBH4> KBH4> LiBH4. The cyanosilylation of acetophenone using trimethylsilyl cyanide (TMSCN) in the presence of NaBH4 occurred under similar reaction conditions. An excellent reaction rate and high conversion were obtained. Conclusion: The metal borohydride-catalyzed hydrosilylation alcohols in one step. The and cyanosilylation of ketones could be carried out smoothly under mild reaction conditions. Among the metal borohydrides studied, an excellent reaction rate and high conversion were obtained using NaBH4, NaBH (CH2CH3)3 or (alkyl)4 NBH4 as the reaction catalyst.


2020 ◽  
Vol 129 (7) ◽  
pp. 869
Author(s):  
В.С. Каплин ◽  
А.С. Копылов ◽  
Т.С. Зархина ◽  
П.С. Тимашев ◽  
А.Б. Соловьева

Multi-ligand phosphor complexes of neodymium acetylacetonate with phenanthroline are synthesized in polymer matrices (oligourethane methacrylate, fluoroplast, polycarbonate) in supercritical carbon dioxide medium. At the same time the role of one of the ligands in such complexes is played by fragments of the polymer matrix. The luminescence spectra of the obtained ternary systems are described. It was shown that the position of the luminescence maxima is bathochromically shifted relative to the binary systems Nd(Acac)3/polymer obtained in a similar way and the magnitude of the shift depends on the nature of the polymer matrix. It was shown that upon the introduction of these components into polymers from a solution, similar phosphor mixed-ligand neodymium complexes do not form. The formation of new structures Nd(Acac)3/Phen/polymer upon impregnation of oligourethane methacrylate with neodymium β-diketonate and phenanthroline in a supercritical CO2 medium was confirmed by the method of differential thermal analysis. The same method confirmed that with the introduction of these components from the solution of the above systems do not form.


ACS Catalysis ◽  
2016 ◽  
Vol 6 (4) ◽  
pp. 2715-2727 ◽  
Author(s):  
Michael B. Griffin ◽  
Glen A. Ferguson ◽  
Daniel A. Ruddy ◽  
Mary J. Biddy ◽  
Gregg T. Beckham ◽  
...  

2019 ◽  
Author(s):  
Shiori Date ◽  
Kensei Hamasaki ◽  
Karen Sunagawa ◽  
Hiroki Koyama ◽  
Chikayoshi Sebe ◽  
...  

<div>We report here a catalytic, Markovnikov selective, and scalable synthetic method for the synthesis of saturated sulfur heterocycles, which are found in the structures of pharmaceuticals and natural products, in one step from an alkenyl thioester. Unlike a potentially labile alkenyl thiol, an alkenyl thioester is stable and easy to prepare. The powerful Co catalysis via a cobalt hydride hydrogen atom transfer and radical-polar crossover mechanism enabled simultaneous cyclization and deprotection. The substrate scope was expanded by the extensive optimization of the reaction conditions and tuning of the thioester unit.</div>


2019 ◽  
Author(s):  
Bella Grigorenko ◽  
Igor Polyakov ◽  
Alexander Nemukhin

<p>We report a mechanism of adenosine triphosphate (ATP) to cyclic adenosine monophosphate (cAMP) conversion by the mammalian type V adenylyl cyclase revealed in molecular dynamics (MD) and quantum mechanics/molecular mechanics (QM/MM) simulations. We characterize a set of computationally derived enzyme-substrate (ES) structures showing an important role of coordination shells of magnesium ions in the solvent accessible active site. Several stable six-fold coordination shells of Mg<sub>A</sub><sup>2+ </sup>are observed in MD simulations of ES complexes. In the lowest energy ES conformation, the coordination shell of Mg<sub>A</sub><sup>2+ </sup>does not include the O<sub>δ1</sub> atom of the conserved Asp440 residue. Starting from this conformation, a one-step reaction mechanism is characterized which includes proton transfer from the ribose O<sup>3'</sup>H<sup>3' </sup>group in ATP to Asp440 via a shuttling water molecule and P<sup>A</sup>-O<sup>3A</sup> bond cleavage and O<sup>3'</sup>-P<sup>A</sup> bond formation. The energy profile of this route is consistent with the observed reaction kinetics. In a higher energy ES conformation, Mg<sub>A</sub><sup>2+</sup> is bound to the O<sub>δ1</sub>(Asp440) atom as suggested in the relevant crystal structure of the protein with a substrate analog. The computed energy profile initiated by this ES is characterized by higher energy expenses to complete the reaction. Consistently with experimental data, we show that the Asp440Ala mutant of the enzyme should exhibit a reduced but retained activity. All considered reaction pathways include proton wires from the O<sup>3'</sup>H<sup>3' </sup>group via shuttling water molecules. </p>


2017 ◽  
pp. 126-169
Author(s):  
S.E. Tariverdieva

The article deals with the development of the coregency system of Augustus and Agrippa from 29 to 18 BC: from formal and actual disparity of the coregents to their formal equality with the dominance of the princeps auctoritas. Particular attention is paid to the earlier stages of this development and to the crisis of 23 BC. The coregency system created by Augustus is often regarded by modern historians as means of ensuring uninterrupted succession of power. Agrippa as his coregent often is thought to have assumed the role of the regent who temporally replaces the princeps, just as it was in formal monarchies, or that of the tutor of the future rulers. However, the Roman system of state administration did not allow such type of regency. The princeps coregent, who was his equal in formal credentials but his inferior in terms of auctoritas, in case of the princeps death had to become the next princeps as his immediate successor. It is unlikely that later he was expected to voluntarily give up his power in favour of younger heir and to vanish from the political life altogether. The inheritance system under Augustus was like a ladder with the princeps at the top, the coregent who was also the immediate successor one step below, heirs of the next degree further down. In case of death of one of them, successors shifted one step up. The coregency had one more function: geographically it allowed Augustus and Agrippa to rule jointly the empire while staying in different parts of it.В статье исследуется развитие системы соправления Августа и Агриппы с 29 по 12 гг. до н. э.: от формального и фактического неравенства соправителей до их формального равенства при преобладании auctoritas принцепса, причём особое внимание уделяется раннему этапу этого развития и кризису 23 г. до н. э. Институт соправления, созданный Августом, часто рассматривается, как средство обеспечения бесперебойного перехода власти, причем Агриппе, как соправителю, НЕРЕДКО отводится роль регента, временно замещающего принцепса или воспитателя будущих правителей. Однако римская система государственного управления не предполагала регентства. Соправитель принцепса, равный ему по формальным полномочиям, но уступавший по auctoritas, в случае его смерти должен был СТАТЬ следующим принцепсом, ближайшим его наследником. Вряд ли предполагалось, что в будущем он должен добровольно уступить власть более молодому наследнику и исчезнуть из политической жизни. Система наследования при Августе представляла собой нечто вроде лестницы, на вершине которой стоял принцепс, на следующей ступени соправитель, он же избранный преемник, ниже наследники следующей очереди в случае смерти когото из них происходило продвижение наследников по ступеням вверх. Кроме того, соправление имело и иное значение позволяло Августу и Агриппе совместно управлять империей, находясь в разных ее частях.


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