- Stabilization of Hydroxynitrile Lyases from Two Variants of Passion Fruit, Passiflora edulis Sims and Passiflora edulis Forma flavicarpa, by C-Terminal Truncation
-
Because the synthesis of chiral compounds generally requires a broad range of substrate specificity and stable enzymes, screening for better enzymes and/or improvement of enzyme properties through molecular approaches is necessary for sustainable industri
- Nuylert, Aem,Motojima, Fumihiro,Khanongnuch, Chartchai,Hongpattarakere, Tipparat,Asano, Yasuhisa
-
p. 181 - 189
(2019/12/12)
-
- Highly chemoselective and efficient Strecker reaction of aldehydes with TMSCN catalyzed by MgI2 etherate under solvent-free conditions
-
Strecker reaction of various substituted aromatic aldehydes, heteroaromatic aldehydes, aliphatic aldehydes and α,β-unsaturated aldehydes with trimethylsilyl cyanide (TMSCN) was realized in the presence of 5 mol % of MgI2 etherate in a mild, efficient and highly chemoselective manner under solvent-free conditions.
- He, Kailun,Liu, Huijun,Zhang, Xingxian,Zhou, Jing
-
supporting information
p. 933 - 936
(2019/03/08)
-
- Postfunctionalized Metalloligand-Based Catenated Coordination Polymers: Syntheses, Structures, and Effect of Labile Sites on Catalysis
-
In this work, pyridyl-appended Co3+ complexes (1 and 2) have been postfunctionalized by using 4-(bromomethyl)benzoic acid, thus changing the functionalities from pyridyl-N donors to carboxylate-O donors. Using two such postfunctionalized metalloligands (3 and 4), several homo and heterometallic coordination polymers (HCPs) have been synthesized. Single crystal structural analyses revealed that all HCPs presented intriguing one-dimensional catenated architectures. Postsynthetic modification induced flexibility was found to be responsible for the nearly identical architectures for two sets of HCPs starting from two different postfunctionalized metalloligands, 3 and 4. Two sets of HCPs differed by the presence (3a-3d) or absence (4a-4b) of labile coordinated water molecules that demonstrated a profound effect on the heterogeneous catalysis of Knoevenagel condensation reactions and cyanation reactions.
- Pandey, Saurabh,Kumar, Girijesh,Gupta, Rajeev
-
p. 2723 - 2735
(2019/05/01)
-
- Hydroxynitrile Lyase Isozymes from Prunus communis: Identification, Characterization and Synthetic Applications
-
Biocatalysts originating from Badamu (Prunus communis) have been applied to catalyze the asymmetric synthesis of (R)-4-methylsulfanylmandelonitrile, a key building block of thiamphenicol and florfenicol. Here, four hydroxynitrile lyase (HNL) isozymes from Badamu were cloned and heterologously expressed in Pichia pastoris. The biochemical properties and catalytic performances of these isozymes were comprehensively explored to evaluate their efficiency and selectivity in asymmetric synthesis. Among then, PcHNL5 was identified with outstanding activity and enantioselectivity in asymmetric hydrocyanation. Under the optimized mild biphasic reaction conditions, seventeen prochiral aromatic aldehydes were converted to valuable chiral cyanohydrins with good yields (up to 94%) and excellent optical purities (up to >99.9% ee), which provide a facile access to numerous chiral amino alcohols, hypoglycemic agents, angiotension converting enzyme (ACE) inhibitors and β-blockers. This work therefore underlines the importance of discovering the most potent biocatalyst among a group of isozymes for converting unnatural substrates into value-added products. (Figure presented.).
- Zheng, Yu-Cong,Xu, Jian-He,Wang, Hui,Lin, Guo-Qiang,Hong, Ran,Yu, Hui-Lei
-
p. 1185 - 1193
(2017/04/13)
-
- Multivariate Metal-Organic Frameworks as Multifunctional Heterogeneous Asymmetric Catalysts for Sequential Reactions
-
The search for versatile heterogeneous catalysts with multiple active sites for broad asymmetric transformations has long been of great interest, but it remains a formidable synthetic challenge. Here we demonstrate that multivariate metal-organic frameworks (MTV-MOFs) can be used as an excellent platform to engineer heterogeneous catalysts featuring multiple and cooperative active sites. An isostructural series of 2-fold interpenetrated MTV-MOFs that contain up to three different chiral metallosalen catalysts was constructed and used as efficient and recyclable heterogeneous catalysts for a variety of asymmetric sequential alkene epoxidation/epoxide ring-opening reactions. Interpenetration of the frameworks brings metallosalen units adjacent to each other, allowing cooperative activation, which results in improved efficiency and enantioselectivity over the sum of the individual parts. The fact that manipulation of molecular catalysts in MTV-MOFs can control the activities and selectivities would facilitate the design of novel multifunctional materials for enantioselective processes.
- Xia, Qingchun,Li, Zijian,Tan, Chunxia,Liu, Yan,Gong, Wei,Cui, Yong
-
supporting information
p. 8259 - 8266
(2017/06/28)
-
- A magnetic nanoparticle catalyzed eco-friendly synthesis of cyanohydrins in a deep eutectic solvent
-
Magnetic Fe3O4 nanoparticles in deep eutectic solvents (DESs) have been regard as excellent catalysts for highly efficient cyanosilylation of various aldehydes and epoxides using trimethylsilyl cyanide TMSCN in high yields with excellent selectivity. Fe3O4 nanoparticles were synthesized and applied as a catalyst for the preparation of a wide variety of cyanohydrins (α-hydroxy nitriles and β-hydroxy nitriles) in readily available urea-choline chloride deep eutectic solvent DES as the most promising environmentally benign and cost-effective green solvent. Magnetic DES operates at very mild reaction conditions and can be easily recycled without significant loss of its catalytic activity.
- Azizi, Najmedin,Rahimi, Zahra,Alipour, Masoumeh
-
p. 61191 - 61198
(2015/07/28)
-
- A metalloligand appended with thiazole rings: Heterometallic {Co3+-Zn2+} and {Co3+-Cd2+} complexes and their heterogeneous catalytic applications
-
This work describes a Co3+-based metalloligand containing appended thiazole rings and its reactions with secondary metal ions to produce heterometallic {Co3+-Zn2+} and {Co3+-Cd2+} complexes. Structural studies show that some of the appended thiazole rings from the metalloligand coordinate to secondary metal ions, whereas the remaining ones act as hydrogen-bond acceptors to metal-bound CH3OH or H2O molecules. These heterometallic complexes function as reusable heterogeneous catalysts for the ring-opening reactions of epoxides as well as cyanation and Knoevenagel condensation reactions of aldehydes. The catalytic results illustrate that the microenvironment remains intact during the catalysis and potentially enhances the substrate interaction with the Lewis acidic secondary metal ions.
- Bansal, Deepak,Hundal, Geeta,Gupta, Rajeev
-
p. 1022 - 1032
(2015/06/24)
-
- Three-Dimensional Heterometallic Coordination Networks: Syntheses, Crystal Structures, Topologies, and Heterogeneous Catalysis
-
This work presents the synthesis of {Co3+-Zn2+} and {Co3+-Cd2+} heterometallic coordination networks. These networks are originated from two unique Co3+-based metalloligands containing appended arylcarboxylic acid groups at the strategically placed positions. Such appended arylcarboxylate groups coordinate the secondary metal ions, Zn2+ and Cd2+, to afford distinct three-dimensional networks. All four networks display orderly arrangement of secondary metal ions and unique network topologies including an unprecedented one. These networks have been shown to act as the heterogeneous and reusable catalysts for the Knoevenagel condensation reactions and cyanation reactions of assorted aldehydes. Cyanation reactions nicely demonstrate the substrate size-exclusion catalysis.
- Srivastava, Sumit,Aggarwal, Himanshu,Gupta, Rajeev
-
p. 4110 - 4122
(2015/08/18)
-
- Enantioselective cyanosilylation of aldehydes catalyzed by novel camphor derived Schiff bases-titanium(IV) complexes
-
Five tridentate Schiff bases have been prepared from (1R,2S,3R,4S)-3-amino- 1,7,7-trimethylbicyclo[2.2.1]heptan-2-ol and salicylaldehydes. X-ray structure investigation revealed differences in their molecular conformation, and their titanium(IV) complexes
- B?ocka, Ewelina,Bosiak, Mariusz J.,We?niak, Miros?aw,Ludwiczak, Agnieszka,Wojtczak, Andrzej
-
p. 554 - 562
(2014/05/06)
-
- Mononuclear complexes of amide-based ligands containing appended functional groups: Role of secondary coordination spheres on catalysis
-
Amide-based ligands H2L1, H2L2 and H2L3 containing thiazole, thiazoline and benzothiazole appended groups have been used to synthesize Zn2+ (1 and 3), Cd2+ complexes (2 and 4), and a Mn2+ complex (5). In all cases, potentially multidentate ligands create a meridional N3 coordination environment around the M(ii) ion whereas additional sites are occupied by labile nitrate ions in 1-4 and MeOH in 5. Interestingly, metal complexation caused the migration of protons from amidic N-H sites to the appended heterocyclic rings in complexes 1-4. Structural studies show that the protonated heterocyclic rings in these complexes create a hydrogen bond based cavity adjacent to the metal ion. Importantly, binding studies confirm that the substrates are bound within the complex cavity closer to the Lewis acidic metal in all complexes including the oxidation-sensitive Mn ion in complex 5. All complexes have been utilized as the reusable and heterogeneous catalysts for ring-opening reactions of assorted epoxides, cyanation reactions of various aldehydes, and epoxidation reactions of several olefins. This journal is
- Bansal, Deepak,Kumar, Gulshan,Hundal, Geeta,Gupta, Rajeev
-
p. 14865 - 14875
(2015/02/19)
-
- Relationships between the racemic structures of substituted mandelic acids containing 8- and 10-membered hydrogen bonded dimer rings
-
The structures of 27 monosubstituted mandelic acids, including several of their polymorphs, plus unsubstituted mandelic acid itself (two polymorphs) are investigated for structural similarity. The results, presented pictorially as a structural relationship plot, show that rather more structures are built up from the carboxyl-chain hydroxyl hydrogen bonded dimer than from the conventional carboxylic acid dimer. The results show how all the structures are related and, based on the two types of dimer, the degree of similarity that they possess. Some structures with Z′ > 1 contain both sorts of dimers and there are many examples of isostructural sets within the structures so far determined. We also present an example where analysing similarity in related families of structures highlights a structure that should be present and which has indeed then proceeded to be synthesised and determined.
- Coles,Ellis,Leung,Sarson,Threlfall,Tizzard
-
p. 10816 - 10823
(2015/02/19)
-
- Three-dimensional {Co3+-Zn2+} and {Co 3+-Cd2+} networks originated from carboxylate-rich building blocks: Syntheses, structures, and heterogeneous catalysis
-
The present work shows the utilization of Co3+ complexes appended with either para- or meta-arylcarboxylic acid groups as the molecular building blocks for the construction of three-dimensional {Co 3+-Zn2+} and {Co3+-Cd2+} heterobimetallic networks. The structural characterizations of these networks show several interesting features including well-defined pores and channels. These networks function as heterogeneous and reusable catalysts for the regio- and stereoselective ring-opening reactions of various epoxides and size-selective cyanation reactions of assorted aldehydes.
- Kumar, Girijesh,Gupta, Rajeev
-
p. 10773 - 10787
(2013/10/22)
-
- A simple separation method for (S)-hydroxynitrile lyase from cassava and its application in asymmetric cyanohydrination
-
Using an acetone precipitation method, crude (S)-hydroxynitrile lyase [(S)-MeHNL] was separated from Munihot esculenta (cassava) leaves, and used directly as biocatalyst to catalyze asymmetric cyanohydrination and produce cyanohydrins with enantiomeric purities (≥90% ee) significantly greater than those previously reported. The use of a water/i-Pr2O system with an enzyme, NaCN, and appropriate amounts of acetic acid is crucial in improving the stereoselectivity of cyanohydrin formation by minimizing the non-enzymatic reaction and the racemization of the chiral products. The proposed isolation method for crude (S)-MeHNL has a high value because of its simplicity, and low cost as well as the high activity of the crude (S)-MeHNL.
- Zheng, Zubiao,Zi, Yan,Li, Zhongzhou,Zou, Xinzhuo
-
p. 434 - 439
(2013/06/27)
-
- NaCN/DOWEX(R)50WX4: A convenient system for synthesis of cyanohydrins from aldehydes
-
A variety of cyanohydrins were prepared from Aldehydes with sodium cyanide and DOWEX(R)50WX4 in a convenient procedure.
- Sofighaderi, Sargol,Setamdideh, Davood
-
p. 1135 - 1137
(2014/03/21)
-
- Cyanative self-condensation of aromatic aldehydes promoted by VO(O iPr)3-Lewis base as a cooperative catalyst
-
Self-condensation of aromatic aldehydes with trimethylsilyl cyanide proceeded by the cooperative catalytic effect of VO(OiPr)3 and a Lewis base to give the corresponding O-acylated cyanohydrins. The reaction conversion and selectivity were strongly dependent on the solvent used, the Lewis base, and the presence of oxygen. All the nine kinds of aromatic aldehydes considered herein afforded the O-acylated cyanohydrins with excellent selectivity under an O2 atmosphere.
- Kodama, Koichi,Kawamata, Hiroaki,Takahashi, Naoya,Hirose, Takuji
-
p. 9440 - 9446
(2013/01/15)
-
- α-Pinene-type chiral Schiff bases as tridentate ligands in asymmetric addition reactions
-
A group of tridentate Schiff bases derived from (+)-α-pinene were synthesized. The steric effects in the transition state, the importance of π-π stacking interactions as well as the electronic effects of aryl aldehydes according to Hammett constant values in the enantioselective addition of Et2Zn to aldehydes with the use of Schiff bases as chiral ligands are described. Also, a variety of aldehydes were cyanated using a catalyst prepared in situ from titanium tetraisopropoxide and chiral Schiff bases. The influence of a conjugated double-bond in the cyanation substrates on enantioselectivity was observed. The chemical structures of the chiral Schiff base-titanium alkoxide complexes are discussed based on their 1H and 13C NMR spectra. 3D models of the Zn2-complex catalyst and Ti-complex catalyst containing α-pinane-type Schiff bases based on X-ray diffraction experiments are postulated. The models presented were consistent with the reported chirality of the addition product and observed ee.
- Jaworska, Magdalena,Blocka, Ewelina,Kozakiewicz, Anna,Welniak, Miroslaw
-
experimental part
p. 648 - 657
(2011/07/08)
-
- Enantioselective silylcyanation of aldehydes catalyzed by new chiral oxovanadium complex
-
Oxovanadium(V) complex 4 was prepared from VOSO4 and tridentate Schiff base ligand, which was prepared from substituted salicylaldehyde and inexpensive (S)-valine. Asymmetric silylcyanation of the aldehydes catalyzed by catalyst 4 afforded cyanohydrins with good enantioselectivities.
- Chu, Chang-Ying,Hsu, Chu-Tin,Lo, Po Hsiang,Uang, Biing-Jiun
-
scheme or table
p. 1981 - 1984
(2012/03/10)
-
- Cooperative thiourea-Bronsted acid organocatalysis: Enantioselective cyanosilylation of aldehydes with TMSCN
-
We report a new thiourea - Bronsted acid cooperative catalytic system for the enantioselective cyanosilylation of aldehydes with yields up to 90% and enantioselectivities up to 88%. The addition of an achiral acid was found to be crucial for high asymmetric induction. Mechanistic investigations using a combination of NMR, ESI-MS, and density functional theory computations (including solvent corrections) at the M06/6-31G(d,p) level of theory suggest that the key catalytic species results from the cooperative interaction of bifunctional thioureas and an achiral acid that form well-defined chiral hydrogen-bonding environments.
- Zhang, Zhiguo,Lippert, Katharina M.,Hausmann, Heike,Kotke, Mike,Schreiner, Peter R.
-
p. 9764 - 9776
(2012/01/03)
-
- Asymmetric cyanohydrin formation from aldehydes catalyzed by manganese Schiff base complexes
-
The catalyst generated in situ from Mn(OAc)2 and a chiral Schiff base ligand exhibited excellent catalytic abilities in asymmetric cyanohydrin formation from aldehydes with sodium cyanide in up to 99% enantioselectivity and good yield.
- Qu, Yanyang,Jing, Linhai,Wu, Zhiqing,Wu, Di,Zhou, Xiangge
-
experimental part
p. 187 - 190
(2010/04/28)
-
- Asymmetric synthesis of a new salen type-titanium complex as the catalyst for asymmetric trimethylsilylcyanation of aldehydes
-
This work describes the asymmetric synthesis of a new salen-type ligand via a Diels-Alder reaction and Curtius rearrangement. The ligand with a norbornane skeleton was used in the trimethylsilylcyanation of aldehydes, but the enantioselectivity was 55%ee. The norborane skeleton was cleaved to destroy this rigidity, and the eanatioselectivity was thereby increased to 85%ee.
- Lin, Zheng-Chang,Chen, Chinpiao
-
experimental part
p. 726 - 737
(2011/04/23)
-
- PROCESS FOR PRODUCTION OF 2-HYDROXY ESTERS
-
The invention provides an easy and simple process for the production of 2-hydroxy esters from cyanohydrins, specifically, a process for the production of 2-hydroxy esters represented by the general formula (1) (exclusive of ethyl 2-hydroxy-4-phenylbutyrate), characterized by introducing an acid into a mixture comprising a cyanohydrin represented by the general formula (2), an alcohol, an organic solvent and water: [Chemical formula 1] R1 -CH(OH)-COOR2 (1) R1 -CH(OH)(CN) (2) wherein R1 is hydrogen, a substituted or unsubstituted aliphatic hydrocarbon group which has 1 to 12 carbon atoms and may contain oxygen, sulfur, or nitrogen, a substituted or unsubstituted alicyclic hydrocarbon group which has 3 to 12 carbon atoms and may contain oxygen, sulfur, or nitrogen, or a substituted or unsubstituted aryl or aralkyl group which has 3 to 14 carbon atoms and may contain oxygen, sulfur, or nitrogen; and R2 is alkyl which has 1 to 12 carbon atoms and may contain oxygen, sulfur, or nitrogen.
- -
-
Page/Page column 11
(2010/11/30)
-
- MORPHOLINE DOPAMINE AGONISTS FOR THE TREATMENT OF PAIN
-
The present invention relates to use of a compound of formula (I), (Ia), or (Ib), wherein A, B, Z, R1and R2 have the meanings given in the specification, as a medicament for the treatment of a number of pain conditions, particularly chronic or nociceptive
- -
-
Page/Page column 36
(2008/12/07)
-
- Design and synthesis of a functionally selective D3 agonist and its in vivo delivery via the intranasal route
-
This paper reports the synthesis and biological activity of a novel series of aryl-morpholine dopamine receptor agonists. Several compounds show high levels of functional selectivity for the D3 over the D2 dopamine receptor. Compound 26 has >1000-fold functional selectivity and has been successfully progressed in vivo using an intranasal delivery route.
- Blagg, Julian,Allerton, Charlotte M.N.,Batchelor, David V.J.,Baxter, Andrew D.,Burring, Denise J.,Carr, Christopher L.,Cook, Andrew S.,Nichols, Carly L.,Phipps, Joanne,Sanderson, Vivienne G.,Verrier, Hugh,Wong, Stephen
-
p. 6691 - 6696
(2008/03/14)
-
- Asymmetric addition of trimethylsilyl cyanide to aldehydes promoted by chiral polymeric vanadium(V) salen complex as an efficient and recyclable catalyst
-
The asymmetric addition of trimethylsilyl cyanide to various aldehydes catalyzed by efficient new vanadyl polymeric salen complexes having 12 repeating salen units was investigated at room temperature. An excellent yield of the trimethylsilylether of cyanohydrins (up to 98%) with high chiral induction (96%) in case of 2-methylbenzaldehyde was achieved in 18 h. The catalyst recovered four times with retention of its performance.
- Khan, Noor-ul H.,Agrawal, Santosh,Kureshy, Rukhsana I.,Abdi, Sayed H.R.,Mayani, Vishal J.,Jasra, Raksh V.
-
p. 2659 - 2666
(2007/10/03)
-
- Synthesis of the bifunctional BINOL ligands and their applications in the asymmetric additions to carbonyl compounds
-
Efficient one-step syntheses of the bifunctional BINOL and H8BINOL ligands (S)-6 and (S)-8 have been developed from the reaction of BINOL and H8BINOL with morpholinomethanol, respectively. The X-ray analyses of these compounds have revealed their structural similarity and difference. The bifunctional H8BINOL (S)-8 is found to be highly enantioselective for the reaction of diphenylzinc with many aliphatic and aromatic aldehydes and especially is the most enantioselective catalyst for linear aliphatic aldehydes. Unlike other catalysts developed for the diphenylzinc addition which often require the addition of a significant amount of diethylzinc with cooling (or heating) the reaction mixture in order to achieve high enantioselectivity, using (S)-8 needs no additive and gives excellent results at room temperature. (S)-8 in combination with diethylzinc and Ti(OiPr)4 can catalyze the highly enantioselective phenylacetylene addition to aromatic aldehydes. It can also promote the phenylacetylene addition to acetophenone at room temperature though the enantioselectivity is not very high yet. Without using Ti(OiPr)4 and a Lewis base additive, (S)-8 in combination with diethylzinc can catalyze the reaction of methyl propiolate with an aldehyde to form the highly functional γ-hydroxy-α,β-acetylenic esters except that the enantioselectivity is low at this stage. The bifunctional BINOL ligand (S)-6 in combination with Me2AlCl is found to be a highly enantioselective catalyst for the addition of TMSCN to both aromatic and aliphatic aldehydes.
- Qin, Ying-Chuan,Liu, Lan,Sabat, Michal,Pu, Lin
-
p. 9335 - 9348
(2007/10/03)
-
- A new (R)-hydroxynitrile lyase from Prunus mume: Asymmetric synthesis of cyanohydrins
-
A new hydroxynitrile lyase (HNL) was isolated from the seed of Japanese apricot (Prunus mume). The enzyme has similar properties with HNL isolated from other Prunus species and is FAD containing enzyme. It accepts a large number of unnatural substrates (benzaldehyde and its variant) for the addition of HCN to produce the corresponding cyanohydrins in excellent optical and chemical yields. A new HPLC based enantioselective assay technique was developed for the enzyme, which promotes the addition of KCN to benzaldehyde in a buffered solution (pH=4.5).
- Nanda, Samik,Kato, Yasuo,Asano, Yasuhisa
-
p. 10908 - 10916
(2007/10/03)
-
- Asymmetric cyanosilylation of aldehydes catalyzed by novel organocatalysts
-
A novel proline-based N,N′-dioxide, which is easily prepared from inexpensive chemicals, serves as an effective catalyst for enantioselective cyanosilylation of aldehydes in up to 73% ee. Georg Thieme Verlag Stuttgart.
- Wen, Yuehong,Huang, Xiao,Huang, Jinglun,Xiong, Yan,Qin, Bo,Feng, Xiaoming
-
p. 2445 - 2448
(2007/10/03)
-
- Highly enantioselective cyanosilylation of aldehydes catalyzed by novel β-amino alcohol-titanium complexes
-
The β-amino alcohol 1b-Ti(Oi-Pr)4 complex has been shown to catalyze the enantioselective cyanosilylation of aldehydes efficiently. In the presence of 5 mol % of 1b-Ti(Oi-Pr)4 complex catalyst, the aromatic, conjugated, heteroaromatic, and aliphatic aldehydes were converted to their corresponding trimethylsilyl ethers of cyanohydrins in 90-99% yields with up to 94% ee under mild conditions.
- Li, Yan,He, Bin,Qin, Bo,Feng, Xiaoming,Zhang, Guolin
-
p. 7910 - 7913
(2007/10/03)
-
- MORPHOLINE DERIVATIVES FOR USE AS DOPAMINE AGONISTS IN THE TREATMENT OF I.A. SEXUAL DYSFUNCTION
-
The present invention provides for compounds of formula (I), (la) and (lb) Wherein: A is selected from C-X and N, B is selected from C-Y and N, R1 is selected from H and (C1-C6)alkyl R2 is selected from H and (C
- -
-
-
- Synthesis of a new chiral cyclic o-hydroxynaphthylphosphonodiamide and its application as ligand catalyst in asymmetric silylcyanation of aromatic aldehydes
-
A new chiral cyclic o-hydroxynaphthylphosphonodiamide (+)-2 was synthesized starting from (+)-cis-1,2,2-trimethylcyclopentane-1,3-diamine. The absolute configuration of phosphorus atom was determined as S by X-ray diffraction analysis. Excellent enantiose
- He, Ke,Zhou, Zhenghong,Wang, Lixin,Li, Kangying,Zhao, Guofeng,Zhou, Qilin,Tang, Chuchi
-
p. 1521 - 1524
(2007/10/03)
-
- Catalysis of aldehyde and imine silylcyanation by platinum and palladium NCN-pincer complexes
-
The room temperature addition of trimethylsilylcyanide to aromatic and aliphatic aldehydes to give the corresponding cyanohydrins is efficiently catalysed by 1 mol% of ((2,6-bis(N-cyclohexyl)imino)phenyl)aquoplatinum(II) trifluoromethanesulfonate 1a. This methodology is also applicable to the addition of trimethylsilylcyanide to Schiff bases resulting in the formation of α-amino nitriles.
- Fossey, John S.,Richards, Christopher J.
-
p. 8773 - 8776
(2007/10/03)
-
- CAL-B catalyzed enantioselective synthesis of cyanohydrins - A facile route to versatile building blocks
-
A straightforward process for the preparation of optically active cyanohydrins, important building blocks for the synthesis of drugs and agrochemicals, has been established. Lipase B from Candida antarctica (CAL-B) catalyzes the kinetic resolution of racemic cyanohydrin acetates under mild conditions: optimization of the process led to a user-friendly synthesis of (S)- and (R)-cyanohydrins.
- Hanefeld,Li,Sheldon,Maschmeyer
-
p. 1775 - 1776
(2007/10/03)
-
- Preparation of optically active cyanohydrins using the (S)-hydroxynitrile lyase from Hevea brasiliensis
-
Several aliphatic, aromatic and heteroaromatic aldehydes have been converted into the chiral cyanohydrins using the (S) hydroxynitrile lyase from Hevea brasiliensis. The corresponding cyanohydrins were obtained in moderate to good yield and high enantiomeric excess with the exeption of phenyloxyacetaldehyde, benzyloxyacetaldehyde and the pyrrole-, pyridine- and indolealdehydes investigated. In contrast to previously reported results, cinnamaldehyde could be converted into (S)-(-)-2-hydroxy-4-phenyl-(E)-but-3- enenitrile with good selectivity by means of optimized reaction conditions.
- Schmidt, Michael,Herve, Stephanie,Klempier, Norbert,Griengl, Herfried
-
p. 7833 - 7840
(2007/10/03)
-
- A catalyst for asymmetric induction
-
A catalyst for asymmetric induction is provided which comprises a titanium (IV) alkoxide and an amino acid amide derivative of formula (I): wherein R1 is isopropyl, isobutyl, sec-butyl, tert-butyl, phenyl or benzyl, R2 and R3 are the same or different and each is lower alkyl, C3 to C8 cycloalkyl, unsubstituted or substituted phenyl or hydrogen or R2 and R3 together form a divalent C3 to C7 alkylene group optionally containing one or more hetero atoms, R4 is chlorine, bromine, iodine, lower alkyl or unsubstituted or substituted phenyl, R5, R6 and R7 are the same or different and each is hydrogen, halogen, methyl or methoxy or R5 is as defined above and R6 and R7 together form -CH=CH-CH=CH- or -OCH2O- or R7 is as defined above and R5 and R6 together form -CH=CH-CH=CH- or -OCH2O- and * denotes an absolute configuration of S or R.
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-
-
- Reductive Coupling of Benzoyl Cyanide and Carbonyl Compounds by Aqueous Ti(III) Ions. A New Convenient and Selective Access to the Less Stable Mixed Benzoins
-
The reactive species formed by the Ti(III) ion reduction of benzoyl cyanide (1) adds to the C-atom of carbonyl compounds 2 under simple experimental conditions.The intermediate 1,2-diols 3 are smoothly converted, without isolation, into the less thermodynamically stable mixed benzoins 4, which are not accessible by the classical benzoin condensation.The possible mechanisms involved in the reaction are discussed.
- Clerici, Angelo,Porta, Ombretta
-
p. 2889 - 2893
(2007/10/02)
-
- Lanthanoid(III) Alkoxides as Novel Catalysts for a Rapid Transhydrocyanation from Acetone Cyanohydrin to Aldehydes and Ketones
-
A rapid transhydrocyanation from acetone cyanohydrin to several aldehydes and ketones is promoted by a catalytic amount of lanthanoid(III) alkoxide to provide the corresponding cyanohydrins.
- Ohno, Hiroshi,Mori, Atsunori,Inoue, Shohei
-
p. 375 - 378
(2007/10/02)
-
- Peptide-titanium complex as catalyst for asymmetric addition of hydrogen cyanide to aldehyde
-
The complex of titanium ethoxide and an acyclic dipeptide ester whose terminal amino group is modified to a salicylal-type Schiff base catalyzes the asymmetric addition of hydrogen cyanide to aldehydes with high enantioselectivity. In the reaction of benzaldehyde and hydrogen cyanide, (R)-mandelonitrile is obtained with an enantiomeric excess of 90% when N-((2-hydroxy-1-naphthyl)methylene)-(S)-valyl-(S)-tryptophan methyl ester is employed. In place of the dipeptide, the amide derivatives of an amino acid modified by substituted salicylaldehyde, such as N-(3,5-dibromosalicylidene)-(S)-valine piperidide, exhibit an entirely opposite stereoselectivity to yield S-cyanohydrins with optical purities up to 97% ee. This novel peptide-titanium complex, therefore, enables us to afford optically active cyanohydrins of both absolute configurations by using natural S-amino acids as chiral auxiliaries.
- Nitta, Hideaki,Yu, Donghai,Kudo, Masanobu,Mori, Atsunori,Inoue, Shohei
-
p. 7969 - 7975
(2007/10/02)
-
- A catalyst for asymmetric induction
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Catalysts for producing optically active cyanohydrins by addition of hydrogen cyanide to aldehydes comprising a titanium (IV) alkoxide and a dipeptide derivative of formula (I) wherein R1 is isopropyl, isobutyl, sec-butyl, tert-butyl, methyl, benzyl or phenyl, R3 is lower alkoxy, hydroxyl or mono- or di-lower alkylamino, and either R4 is hydrogen and R2 is benzyl, indol-3-ylmethyl, isopropyl, isobutyl, or phenyl, or R2 and R4 together form -CH2-CH=CH- or -CH=CH-CH2-, R5, R6, R7 and R8 are the same or different and each is hydrogen, halogen, lower alkyl or lower alkoxy, or R5 and R6 or R6 and R7, or R7 and R8 together form -CH=CH-CH=CH- or -OCH2O-, and * denotes an asymmetric carbon atom having an absolute configuration of S or R.
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- A Novel Rate Enhancement in Titanium and Zirconium Alkoxide Mediated Cyano Group Transfer by the Addition of Salycylal Type Schiff Base, dl-3-(2-Hydroxy-1-naphthylidene)-imino ε-caprolactame. A Neighboring Amide Effect
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The addition of a salycylal type Schiff base containing amide, dl-3-(2-hydroxy-1-naphthylidene)imino-ε-caprolactam (Nap-ACL) to titanium (IV) 2-propoxide or zirconium (IV) 1-propoxide accelerates cyano group transfers of acetone cyanohydrin with various carbonyl and imino compounds to give the corresponding cyanated products.
- Mori, Atsunori,Inoue, Shohei
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p. 145 - 148
(2007/10/02)
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- ENZYME-CATALYZED SYNTHESIS OF (S)-CYANOHYDRINS AND SUBSEQUENT HYDROLYSIS TO (S)-α-HYDROXY-CARBOXYLIC ACIDS
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(S)-Cyanohydrins 2 are obtained with high enantioselectivity from aromatic aldehydes and HCN in the presence of (S)-oxynitrilase (E.C.4.1.2.11).Acid-catalyzed hydrolysis of the cyanohydrins 2 affords the corresponding (S)-α-hydroxy carboxylic acids 3 without racemization.
- Effenberger, Franz,Hoersch, Brigitte,Foerster, Siegfried,Ziegler, Thomas
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p. 1249 - 1252
(2007/10/02)
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- A General Synthesis of 3,5-Dihalo-2H-1,4-oxazin-2-ones from Cyanohydrins
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In a novel approach starting from O-trimethylsilyl protected or unprotected cyanohydrins and oxalyl chloride or bromide, a series of unknown 6-substituted 3,5-dihalo-2H-1,4-oxazin-2-ones were prepared.The method was shown to be efficient for various types of cyanohydrins; however cyclization was not obtained with cyanohydrins containing bulky substituents, electron-rich aryl or heteroaryl groups.A mechanism is proposed.
- Meerpoel, Lieven,Hoornaert, Georges
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p. 905 - 908
(2007/10/02)
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- Cyano Group Transfer of Acetone Cyanohydrin to Aldehyde Mediated by Titanium Alkoxide and Aluminum Alkyls
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Cyano group transfer reaction of acetone cyanohydrin to various aldehydes in the presence of titanium alkoxide and aluminum alkyls to give the corresponding aldehyde cyanohydrins in high yield is described.
- Mori, Atsunori,Kinoshita, Koichi,Osaka, Masahiko,Inoue, Shohei
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p. 1171 - 1172
(2007/10/02)
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- Enzymatic Preparation of Optically Active Cyanohydrin Acetates
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A series of cyanohydrin acetates (1)-(47) of widely varying structures, potential chiral building blocks for numerous synthetic applications, has been prepared in good chemical and often high optical yields by enzymatic hydrolysis of their racemic acetates in the presence of an ester hydrolase from Pseudomonas sp.
- Almsick, Andreas van,Buddrus, Joachim,Hoenicke-Schmidt, Petra,Laumen, Kurt,Schneider, Manfred P.
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p. 1391 - 1393
(2007/10/02)
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- Cyclo-((S)-leucyl-(S)-histidyl). A Catalyst for Asymmetric Addition of Hydrogen Cyanide to Aldehydes
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Asymmetric addition of hydrogen cyanide to various aldehydes in the presence of a catalytic amount of cyclo-((S)-leucyl-(S)-histidyl) affords the corresponding cyanohydrins in moderate to good optical yields.The reaction of benzaldehyde with hydrogen cyanide gives (S)-2-hydroxy-2-phenylacetonitrile (85percent, 55percent ee) whose stereochemistry is found to be opposite to our previous result using cyclo-((S)-phenylalanyl-(S)-histidyl).
- Mori, Atsunori,Ikeda, Yoshitaka,Kinoshita, Koichi,Inoue, Shohei
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p. 2119 - 2122
(2007/10/02)
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- Asymmetric Hydrocyanation of a Range of Aromatic and Aliphatic Aldehydes
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A range of aryl, alkyl and heterocyclic aldehydes have been treated with hydrogen cyanide in the presence of the 'Inoue' catalyst, (R,R)- or (S,S)-cyclo.Most aryl aldehydes with electron-donating substituents in the m-or p-positions give high enantiomeric excess (e.e) values (>=80percent) but aryl aldehydes with strong electron-withdrawing substituents gave moderate e.e. values (=50percent).These moderate values are believed to be due to partial racemization of the product cyanohydrins in the presence of the mildly basic catalyst.In contrast to the reactions of aryl aldehydes, reactions of alkyl aldehydes and of ketones gave low e.e. values (=30percent) and an explanation is proposed.
- Matthews, Barry R.,Jackson, W. Roy,Jayatilake, Gamini S.,Wilshire, Colin,Jacobs, Howard A.
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p. 1697 - 1710
(2007/10/02)
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