The Experts below are selected from a list of 1608 Experts worldwide ranked by ideXlab platform
Roger A Sheldon - One of the best experts on this subject based on the ideXlab platform.
-
lipase catalyzed reactions in ionic liquids
Organic Letters, 2000Co-Authors: Madeira R Lau, F Van Rantwijk, Roger A SheldonAbstract:Candida antarctica lipase was shown to catalyze alcoholysis, ammoniolysis, and perhydrolysis reactions using the ionic liquids 1-butyl-3-methylimidazolium tetrafluoroborate or hexafluorophosphate as reaction media. Reaction rates were generally comparable with, or better than, those observed in organic media.
-
dynamic kinetic resolution of phenylglycine esters via lipase catalysed Ammonolysis
Tetrahedron-asymmetry, 1999Co-Authors: M A Wegman, F Van Rantwijk, M A P J Hacking, J Rops, Pedro C Pereira, Roger A SheldonAbstract:Abstract Ammonolysis of d , l -phenylglycine methyl ester catalysed by Novozym 435 at 40°C in tert -butyl alcohol gave d -phenylglycine amide in 78% ee at 46% conversion, corresponding to an enantiomeric ratio ( E ) of 16. Lowering the temperature improved the enantioselectivity ( E =52 at −20°C). Combination of Ammonolysis with pyridoxal-catalysed in situ racemisation of the unconverted ester (dynamic kinetic resolution), at −20°C, gave d -phenylglycine amide with 88% ee at 85% conversion. The amide racemised much slower than the ester at this low temperature.
-
lipase catalysed ammoniolysis of lipids a facile synthesis of fatty acid amides j mol catal b 1 1996 109 113
Journal of Molecular Catalysis B-enzymatic, 1996Co-Authors: M. C. De Zoete, Alida C. Kock-van Dalen, Fred Van Rantwijk, Roger A SheldonAbstract:Abstract Ammoniolysis of triglycerides to the corresponding fatty acid amides is efficiently catalysed by Candida antarctica lipase (Novozym 435). Thus, olive oil gave 90% of nearly pure oleamide after 72 h at 60 °C. Jojoba wax was similarly converted into a mixture of cis -11-eicosenamide and erucamide together with cis -11-eicosenol and cis -13-docosenol.
-
a new enzymatic reaction enzyme catalyzed Ammonolysis of carboxylic esters
Biocatalysis, 1994Co-Authors: M. C. De Zoete, F Van Rantwijk, A Kockvan C Dalen, Roger A SheldonAbstract:A new enzymatic reaction of carboxylic esters and ammonia (Ammonolysis) was studied. This reaction provides a synthetically useful and mild alternative for the synthesis of amides. Several lipases and one esterase acted as catalyst. Ammonolysis of esters of chiral carboxylic acids gave higher ee values than hydrolysis under comparable reaction conditions. Furthermore, consecutive enzymatic esterification and Ammonolysis provided a convenient one-pot synthesis of carboxylic amides from carboxylic acids.
Yu-rong Yang - One of the best experts on this subject based on the ideXlab platform.
-
short synthesis of the monoterpene indole alkaloid arbornamine
Journal of Organic Chemistry, 2018Co-Authors: Yu Zheng, Bei-bei Yue, Kun Wei, Yu-rong YangAbstract:The first total synthesis of the monoterpene indole alkaloid (±)-arbornamine (1) has been completed, which proceeds in only 6 steps and 31% overall yield from three readily available, known compounds. The synthesis features a cascade involving a Pictet–Spengler cyclization/intramolecular Ammonolysis to create the tetracyclic core of arbornamine (1) in a single chemical operation. The subsequent elaboration of 5 into 1 was effected by a key reductive Heck reaction and global reduction.
-
Short Synthesis of the Monoterpene Indole Alkaloid (±)-Arbornamine
2018Co-Authors: Yu Zheng, Bei-bei Yue, Kun Wei, Yu-rong YangAbstract:The first total synthesis of the monoterpene indole alkaloid (±)-arbornamine (1) has been completed, which proceeds in only 6 steps and 31% overall yield from three readily available, known compounds. The synthesis features a cascade involving a Pictet–Spengler cyclization/intramolecular Ammonolysis to create the tetracyclic core of arbornamine (1) in a single chemical operation. The subsequent elaboration of 5 into 1 was effected by a key reductive Heck reaction and global reduction
Hyett G - One of the best experts on this subject based on the ideXlab platform.
-
Demonstration of Visible Light-Activated Photocatalytic Self-Cleaning by Thin Films of Perovskite Tantalum and Niobium Oxynitrides
'American Chemical Society (ACS)', 2020Co-Authors: Iborra-torres A, An Kulak, Rg Palgrave, Hyett GAbstract:Metal oxynitrides adopting the perovskite structure have been shown to be visible light-activated photocatalysts, and therefore, they have potential as self-cleaning materials where surface organic pollutants can be removed by photomineralization. In this work, we establish a route for the deposition of thin films for seven perovskite oxynitrides, CaTaO2N, SrTaO2N, BaTaO2N, LaTaON2, EuTaO2N, SrNbO2N, and LaNbON2, on quartz and alumina substrates using dip-coating of a polymer gel to form an amorphous oxide precursor film, followed by Ammonolysis. The initially deposited oxide films were annealed at 800 °C, followed by Ammonolysis at temperatures from 850 to 1000 °C. The perovskite oxynitride thin films were characterized using XRD and EDX, with band gaps determined using Tauc plots derived from UV–vis spectroscopic data. A cobalt oxide co-catalyst was deposited onto each film by drop casting, and the photocatalytic activity assessed under visible light using dichloroindophenol dye degradation in the presence of a sacrificial oxidant. The light source used was a solar simulator equipped with a 400 nm cut-off filter. The dye degradation test demonstrated photocatalytic activity in all samples except EuTaO2N and BaTaO2N. The three most active samples were SrNbO2N, CaTaO2N, and SrTaO2N. The cobalt oxide loading was optimized for these three films and found to be 0.3 μg cm–2. Further, catalytic tests were conducted using stearic acid degradation, and this found the film of SrNbO2N with the cobalt oxide co-catalyst to be the most active for complete mineralization of this model pollutant
-
Observation of visible light activated photocatalytic degradation of stearic acid on thin films of tantalum oxynitride synthesized by aerosol assisted chemical vapour deposition
'Royal Society of Chemistry (RSC)', 2019Co-Authors: Sd Cosham, An Kulak, Hyett GAbstract:UV activated photocatalysts deposited using chemical vapour deposition have found commercial success as self-cleaning coatings. However, only limited work has been conducted on the use of the more recently discovered visible light activated photocatalysis for this application. Tantalum oxynitride is an established visible light photocatalyst, and in this paper we have investigated the ability of thin films of tantalum oxynitride to photocatalytically degrade a model organic pollutant, stearic acid, and therefore assess the coatings potential for self-cleaning applications. Thin films of tantalum oxide were formed using aerosol assisted chemical vapour deposition (AACVD) of tantalum ethoxide, and then converted into tantalum oxynitride through Ammonolysis at temperatures between 550 °C and 750 °C. Investigation of the films using XRD, UV-vis spectroscopy and XAFS identify that amorphous tantalum oxynitride is formed during the Ammonolysis, with complete conversion to TaON under conditions of 700 °C for 24 hours. The self-cleaning ability of this film was assessed using stearic acid as the model pollutant, with a degradation rate of 2.5(2) × 1013 molecules per min per cm2 when exposed to a 5-sun solar simulator, equipped with a UV cut-off filter. We therefore conclude that tantalum oxynitride thin films are able to act as self-cleaning coatings through visible light photocatalysis and that films of tantalum oxynitride can be synthesized using a scalable chemical vapour deposition route
Vicente Gotor - One of the best experts on this subject based on the ideXlab platform.
-
synthesis of r 3 4 diaminobutanoic acid by desymmetrization of dimethyl 3 benzylamino glutarate through enzymatic Ammonolysis
Journal of Organic Chemistry, 2003Co-Authors: Monica Lopezgarcia, Igancio Alfonso, Vicente GotorAbstract:Lipase B from Candida antarctica is shown to be a highly efficient catalyst for the desymmetrization of dimethyl 3-(benzylamino)glutarate (1) through aminolysis and Ammonolysis reactions. Using this procedure, enantiopure monoamides are obtained in high yield. The synthetic value of these compounds is demonstrated by the preparation of an enantiopure nonnatural amino acid, i.e. (R)-3,4-diaminobutanoic acid [(+)-12].
-
non conventional hydrolase chemistry amide and carbamate bond formation catalyzed by lipases
Bioorganic & Medicinal Chemistry, 1999Co-Authors: Vicente GotorAbstract:Biocatalysis in nonaqueous media is becoming increasingly important in organic synthesis. Lipases are the most used enzymes, especially in transesterification reactions. However, in the last years the amidation reaction catalyzed by lipases has also been shown to be a useful tool for the organic chemists. In this review, we discuss the possibilities of the enzymatic aminolysis and Ammonolysis reactions for the preparation of different amides and for the resolution of esters, amines and aminoalcohols. The enzymatic alkoxycarbonylation of amines opens a new way for the synthesis of chiral carbamates.
Yu Zheng - One of the best experts on this subject based on the ideXlab platform.
-
short synthesis of the monoterpene indole alkaloid arbornamine
Journal of Organic Chemistry, 2018Co-Authors: Yu Zheng, Bei-bei Yue, Kun Wei, Yu-rong YangAbstract:The first total synthesis of the monoterpene indole alkaloid (±)-arbornamine (1) has been completed, which proceeds in only 6 steps and 31% overall yield from three readily available, known compounds. The synthesis features a cascade involving a Pictet–Spengler cyclization/intramolecular Ammonolysis to create the tetracyclic core of arbornamine (1) in a single chemical operation. The subsequent elaboration of 5 into 1 was effected by a key reductive Heck reaction and global reduction.
-
Short Synthesis of the Monoterpene Indole Alkaloid (±)-Arbornamine
2018Co-Authors: Yu Zheng, Bei-bei Yue, Kun Wei, Yu-rong YangAbstract:The first total synthesis of the monoterpene indole alkaloid (±)-arbornamine (1) has been completed, which proceeds in only 6 steps and 31% overall yield from three readily available, known compounds. The synthesis features a cascade involving a Pictet–Spengler cyclization/intramolecular Ammonolysis to create the tetracyclic core of arbornamine (1) in a single chemical operation. The subsequent elaboration of 5 into 1 was effected by a key reductive Heck reaction and global reduction