- London Dispersion Interactions Rather than Steric Hindrance Determine the Enantioselectivity of the Corey–Bakshi–Shibata Reduction
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The well-known Corey–Bakshi–Shibata (CBS) reduction is a powerful method for the asymmetric synthesis of alcohols from prochiral ketones, often featuring high yields and excellent selectivities. While steric repulsion has been regarded as the key director of the observed high enantioselectivity for many years, we show that London dispersion (LD) interactions are at least as important for enantiodiscrimination. We exemplify this through a combination of detailed computational and experimental studies for a series of modified CBS catalysts equipped with dispersion energy donors (DEDs) in the catalysts and the substrates. Our results demonstrate that attractive LD interactions between the catalyst and the substrate, rather than steric repulsion, determine the selectivity. As a key outcome of our study, we were able to improve the catalyst design for some challenging CBS reductions.
- Eschmann, Christian,Song, Lijuan,Schreiner, Peter R.
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supporting information
p. 4823 - 4832
(2021/02/01)
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- Synthesis of Trihalomethyl Ketones from Trihalomethyl Carbinols (Hal = Cl, Br) Using 2-Iodoxybenzoic Acid
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Abstract: An efficient method for the preparation of trihalomethyl (Cl, Br) ketones by the oxidation of trihalomethyl carbinols with 2-iodoxybenzoic acid in tert-butanol under heating has been developed. A series of trihalomethyl ketones have been synthesized through a simple, convenient, and environmentally friendly method with excellent yields.
- Gulizhabaier,Rexit
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p. 809 - 815
(2021/06/12)
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- Metal-Free Decarboxylative Trichlorination of Alkynyl Carboxylic Acids: Synthesis of Trichloromethyl Ketones
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2,2,2-Trichloroacetophenone derivatives were synthesized via decarboxylative trichlorination from arylpropiolic acids and trichloroisocyanuric acid (TCCA). The reaction was performed in the presence of water at room temperature, and the desired products were obtained in good yields. The reaction showed good functional group tolerance towards halide, cyano, nitro, ketone, ester and aldehyde groups. In addition, the 2,2,2-trichloroacetophenone derivatives were readily transformed into esters, amides, and hydrazides. Based on experiments with H218O (water-18O), we proposed a cationic reaction pathway as the mechanism and suggested two different pathways for producing aryl- and alkyl-substituted propiolic acids. (Figure presented.).
- Jayaraman, Aravindan,Cho, Eunjeong,Irudayanathan, Francis Mariaraj,Kim, Jimin,Lee, Sunwoo
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p. 130 - 141
(2017/12/26)
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- Continuous flow reaction system for the synthesis of 2,2,2-trichloroacetophenone derivatives and its application
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A continuous flow reaction system was developed for the synthesis of 2,2,2-trichloroacetophenone derivatives. When aryl propiolic acids and water were mixed with trichloroisocyanuric acid in DMF at 5 °C, the 2,2,2-trichloroacetophenone derivatives were formed within 5 min with good yields. In addition, the resulting mixture was flowed to react with amines to give the corresponding benzamide. This flow reaction system provided higher yields within shorter times than the batch reaction system.
- Ko, Byeng Ha,Yu, Subeen,Song, Kwang Ho,Lee, Sunwoo
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p. 991 - 994
(2018/02/14)
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- A study on reactions of an alkynylsilane with oxone-KX (X = Cl, Br, I) and its one-pot transformation into an amide/ester
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Oxyhalogenation reactions of a variety of alkynylsilanes were studied using oxone as mild oxidant and KCl, KBr, and KI as halogen sources. In this study, reaction of an alkynylsilane with oxone-KX (X = Cl or Br) produced trichloromethyl/tribromomethyl ketones inhigh yields. Under similar conditions, however, reactions of alkynylsilanes with oxone-KI were found to give exclusively 1,2,2-triiodovinyl derivatives in high yields. In this study, new methods were deveoped for effcient one-pot tranformation of alkynylsilanes into amides and esters by reaction with amines and alcohols respectively via trihalomethyl ketone.
- Sriramoju, Vinodkumar,Jillella, Raveendra,Kurva, Srinivas,Madabhushi, Sridhar
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supporting information
p. 560 - 562
(2017/03/30)
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- A novel β-(oxy)alkyl radical during copper(I)-mediated stereoselective synthesis of (Z)-ene-1,4-diones in a reaction of 2,2,2-trichloro-1-phenylethanone
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A novel β-(oxy)alkyl radical derived from trichloro methyl compound containing neither a suitably located C-C multiple bond nor a leaving group or a H-atom at the β-position of the radical in a reaction of 2,2,2-trichloro-1-phenyl-ethanone with 2 mol equiv each of CuCl and bpy in refluxing DCE under a N2 atm underwent intramolecular heterolysis (just like formation of intact radical cation-anion pair) during stereoselective radical dimerization to Z-ene-1,4-dione along with small amount of reductive dechlorination product. The stereochemistry was established by X-ray diffraction spectroscopy of various solid crystalline products.
- Ram, Ram N.,Tittal, Ram K.
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p. 2437 - 2440
(2016/05/19)
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- Palladium catalyzed addition of arylboronic acid or indole to nitriles: Synthesis of aryl ketones
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Aryl ketones can be synthesized conveniently by a palladium catalyzed addition of arylboronic acid to nitriles in aqueous triflic acid. This catalytic system was extended to the addition of unprotected indoles to nitriles under a slightly modified condition to produce 3-acyl indoles in good yields.
- Das, Tuluma,Chakraborty, Amarnath,Sarkar, Amitabha
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supporting information
p. 7198 - 7202
(2015/01/09)
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- Trichloromethyl ketones: Asymmetric transfer hydrogenation and subsequent Jocic-type reactions with amines
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Amino-amides are important pharmaceutical building-blocks. The enantioselective reduction of trichloromethyl ketones using ruthenium transfer hydrogenation catalysts is reported. The products react in a range of Jocic-type reactions to give enantiomerically enriched amino-amides.
- Perryman, Michael S.,Harris, Matthew E.,Foster, Jade L.,Joshi, Anushka,Clarkson, Guy J.,Fox, David J.
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p. 10022 - 10024
(2013/10/22)
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- Transition-metal-free transformation of aryl bromides into aromatic esters and amides via aryl trichloromethyl ketones
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A variety of aryl bromides have been treated with Mg and then chloral, followed by tBuOCl and subsequently alcohols or amines to produce the corresponding aromatic esters or amides in good yields via the formation of aryl trichloromethyl ketones as intermediates. These reactions are examples of a transition-metal-free one-pot preparation of aromatic esters and amides from aryl bromides. Aryl bromides have been treated with Mg and then chloral, followed by tBuOCl or tBuOCl with I2 as an additive, and subsequently alcohols or amines to form the corresponding aromatic esters and aromatic amides via aryl trichloromethyl ketones as intermediates. Copyright
- Dohi, Souya,Moriyama, Katsuhiko,Togo, Hideo
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p. 7815 - 7822
(2013/12/04)
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- Platinum on carbon-catalyzed precise reduction control of trichloromethyl to Geminal-dichloromethyl groups
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Geminal-dichloromethyl derivatives could be efficiently synthesized by the highly chemoselective platinum on carbon-catalyzed mono-dechlorination of trichloromethyl substrates in dimethylacetamide (DMA) as a specific solvent at 25 °C under a hydrogen atmosphere. Copyright
- Imanishi, Takahiro,Fujiwara, Yuta,Sawama, Yoshinari,Monguchi, Yasunari,Sajiki, Hironao
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p. 771 - 776
(2012/06/30)
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- Unusual reactions of Grignard reagents toward fluoroalkylated esters
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Fluorine-containing esters were demonstrated to be convenient substrates for construction of the corresponding ketones by low temperature reaction with Grignard reagents followed by warming up to 0 °C, while heating the mixture up to 80 °C readily promoted the reduction of the ketones obtained by the generated magnesium alkoxides whose mechanism was speculated as Meerwein-Ponndorf-Verley type reduction by computational technique.
- Yamazaki, Takashi,Terajima, Tsukasa,Kawasaki-Taskasuka, Tomoko
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p. 2419 - 2424
(2008/09/18)
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- A practical asymmetric synthesis of homochiral α-arylglycines
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Enantioselective reduction of a series of substituted aryl trichloromethyl ketones with the CBS-catecholborane reagent afforded homochiral aryl trichloromethyl carbinols which have been elaborated to give homochiral α-arylglycines in high e.e.
- Mellin-Morliere, Christelle,Aitken, David J.,Bull, Steven D.,Davies, Stephen G.,Husson, Henri-Philippe
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p. 149 - 155
(2007/10/03)
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- Two Classes of Enzymes of Opposite Stereochemistry in an Organism: One for Fluorinated and Another for Nonfluorinated Substrates
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Reduction of methyl ketones by dried cells of Geotrichum candidum (APG4) afforded (S)-alcohols in excellent enantiomeric excess (ee), whereas the reduction of trifluoromethyl ketones gave the corresponding alcohols of the opposite configuration also in excellent ee. The replacement of the methyl moiety with a trifluoromethyl group alters both the bulkiness and the electronic properties, the effect of which on the stereoselectivity was examined. No inversion in stereochemistry was observed in the reduction of hindered ketones such as isopropyl ketone, while the stereoselectivity was inverted in the reduction of ketones with electron-withdrawing atoms such as chlorine. The mechanism for the inversion in stereochemistry was investigated by enzymatic studies. Several enzymes with different stereoselectivities were isolated; one of them catalyzed the reduction of methyl ketones, and another with the opposite stereoselectivity catalyzed the reduction of trifluoromethyl ketones. Furthermore, both APG4 and the isolated enzyme were applied to the reduction of fluorinated ketones on a preparative scale, which resulted in the synthesis of chiral fluorinated alcohols with excellent ee.
- Matsuda, Tomoko,Harada, Tadao,Nakajima, Nobuyoshi,Itoh, Toshiyuki,Nakamura, Kaoru
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p. 157 - 163
(2007/10/03)
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- Direct electroreduction or use of an electrogenerated base : Two ways for the coupling of polyhalogenated compounds with aldehydes or ketones
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The electrochemical coupling of polyhalogenated compounds with carbonyl compounds is achieved in two ways. A carbanion RX(n)- is generated either by the direct electroreduction of RX(n)Cl or by deprotonation of RX(n)H. In this latter case the base Ph- is electrogenerated by reduction of iodobenzene. All electrolysis were carried out in an undivided cell fitted with a cadmium-coated cathode and an aluminium or magnesium sacrificial anode.
- Barhdadi, Rachid,Simsen, Blandine,Troupel, Michel,Nedelec, Jean-Yves
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p. 1721 - 1728
(2007/10/03)
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- REACTIONS OF HALOGEN-CONTAINING O-SILYLATED ENOLATES. VI. HALOGENATION OF HALOGEN-CONTAINING O-SILYLATED ENOLATES
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The chlorination of halogen-containing O-silylated enolates prepared from aldehydes leads to formation of stable 1,2-addition products: halogen-substituted 1-(trimethylsiloxy)alkanes.The corresponding bromination products are less stable, and their stabil
- ShChepin, V. V.,Petukhova, I. Yu.,Russkikh, N. Yu.
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p. 2382 - 2385
(2007/10/02)
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- Selected Methods for the Oxidation of 1,1,1-Trichloro-2-alkanols. An Efficient Modification Using Chromic Acid
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The effectiveness of thirteen largely applied procedures has been checked in the oxidation of 1,1,1-trichloropropan-2-ol.A new, simple, and efficient modification using chromic acid has been found for the preparation of representative trichloromethyl ketones.
- Gallina, Carlo,Giordano, Cesare
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p. 466 - 468
(2007/10/02)
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- Kinetic and Thermodynamic Parameters for the Alcoholysis of 2,2,2-Trichloro-1-arylethanones
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The reactions of 2,2,2-trichloro-1-phenylethanone (1a) and 2,2,2-trichloro-1-(p-chlorophenyl)-ethanone (1b) with MeOH, EtOH, n-PrOH, and n-BuOH in the presence of ethylamine resulted in the formation of the corresponding esters ArCOOR.When the process is carried out in the absence of ethylamine the reaction does not proceed beyond formation of the hemiacetal intermediate.The former reaction occurs through an addition-elimination process and the order of reactivity of the alcohols is MeOH>EtOH>n-PrOH>n-BuOH.If (1a or b) is treated with ethylamine in dioxane the corresponding amide ArCONHEt is the only reaction product.
- Uieara, Marina,Zucco, Cesar,Zanette, Dino,Rezende, Marcos C.,Nome, Faruk
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p. 175 - 180
(2007/10/02)
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- Mechanistic Studies on the Basic Hydrolysis of 2,2,2-Trichloro-1-arylethanones
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The basic hydrolysis of 2,2,2-trichloro-1-phenylethanone (1a), 2,2,2-trichloro-1-(p-methoxyphenyl)ethanone (1b), and 2,2,2-trichloro-1-(p-chlorophenyl)ethanone (1c) has been studied in the pH range 5.5-13.2.In all cases the reaction products were chloroform and the corresponding benzoate.The reaction is first order toward both the ethanone and hydroxide ion and proceeds via an addition-elimination-type mechanism.The initial addition step forms the corresponding ethanone hydrates, which, depending on the pH, will form the mono- and dianionic intermediates, the elimination of CCl3 from the mono- and/or dianionic species being the rate-limiting step of the reaction.
- Zucco, Cesar,Lima, Claudio F.,Rezende, Marcos C.,Vianna, Jose F.,Nome, Faruk
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p. 5356 - 5359
(2007/10/02)
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- The α-Chlorination of Aryl Ketones with Manganese(III) Acetate in the presence of Chloride Ion
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The reaction of 2-(4-methoxyphenyl)-4-chromanone with Mn(OAc)3 in the presence of LiCl gave 3,3-dichloro-2-(4-methoxyphenyl)-4-chromanone.The reactions of 2-phenyl-4-chromanone, 1-phenyl-1-propanone, 1,2-diphenylethanone, and 1-tetralone similarly yielded α,α-dichloro derivatives in good yields. 2,2,2-Trichloroacetophenones were obtained from 2,2-dichloroacetophenones, but in the absence of LiCl, 2,2-dichloroacetophenones gave 2,2,3,3-tetrachloro-1,4-butanediones.KCl, NaCl, NH4Cl,AlCl3, and CaCl2 were also employed as the Cl- ion source.Synthetic applicability and the reaction mechanisms are discussed briefly.
- Tsuruta, Takehiko,Harada, Tetsuya,Nishino, Hiroshi,Kurosawa, Kazu
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p. 142 - 145
(2007/10/02)
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- Anomalous Michaelis-Becker Reaction: 1-Phenylethan-1,2,2-triphosphonic Acid and their Esters
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Sodium dialkylphosphite reacts with trichlorovinylbenzene to yield in an one-batch procedure 1-phenyl-1,2,2-ethanetriphosphonic acid hexaalkyl esters.A carbanionic intermediate of an "anomalous Michaelis-Becker reaction" is deduced.Acidolysis of esters leads to the parent triphosphonic acids.NMR parameters of this acid are strongly influenced by protolytic equilibrium. - Key words: One-batch synthesis, Oligophosphonic Acid, NMR Spectra
- Fischer, Ulrich,Haegele, Gerhard
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p. 1152 - 1156
(2007/10/02)
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- CHLORINATION OF KETONES WITH TRICHLOROISOCYANURIC ACID
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Trichloroisocyanuric acid is an effective reagent for the chlorination of ketones in the alpha position.
- Hiegel, Gene A.,Peyton, Kim B.
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p. 385 - 392
(2007/10/02)
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- CONVERSION OF RACEMIC CYANOHYDRIN INTO ONE OPTICALLY ACTIVE ISOMER IN THE PRESENCE OF BRUCINE
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When a solution of a cyanohydrin and brucine in methanol was kept at room temperature, one optically active isomer of the cyanohydrin was obtained as brucine complex in a yield of more than 50percent.
- Toda, Fumio,Tanaka, Koichi
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p. 661 - 664
(2007/10/02)
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- NOVEL SELECTIVE SYNTHESIS OF α-CHLOROMETHYL, α,α-DICHLOROMETHYL, AND α,α,α-TRICHLOROMETHYL KETONES FROM ALDEHYDE UTILIZING ELECTROREDUCTION AS KEY REACTIONS
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A variety of α-chloromethyl, α,α-dichloromethyl, and α,α,α-trichloromethyl ketones were synthesized from aldehyde utilizing cathodic reduction as key reactions.
- Shono, Tatsuya,Kise, Naoki,Yamazaki, Akira,Ohmizu, Hiroshi
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p. 1609 - 1612
(2007/10/02)
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- Photo-CIDNP Observed in O-Methylbenzoin-Carbon Tetrachloride System
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Photo-induced decomposition of O-methylbenzoin in carbon tetrachloride was investigated.A reaction scheme is proposed with the aid of photo-CIDNP technique and product analysis.
- Maruyama, Kazuhiro,Furuta, Hiroyuki,Otsuki, Tetsuo
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p. 2421 - 2422
(2007/10/02)
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