- Organocatalytic Enantioselective Vinylogous Aldol Reaction of Allyl Aryl Ketones to Activated Acyclic Ketones
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The first catalytic asymmetric vinylogous aldol reaction of activated allyls to activated acyclic ketones is disclosed. A variety of activated acyclic ketones, such as trifluoromethyl ketones, α-ketoesters, and α-keto phosphonates, were found to be involved forming diverse γ-selective aldol adducts with high enantioselectivities (up to >99% ee). The method provides an effective, general strategy to access valuable chiral electron-withdrawing group-substituted tertiary hydroxyl-based carboxylic acids.
- Jing, Zhenzhong,Bai, Xiangbin,Chen, Wenchao,Zhang, Gao,Zhu, Bo,Jiang, Zhiyong
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p. 260 - 263
(2016/02/03)
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- Asymmetric 1,2-Perfluoroalkyl Migration: Easy Access to Enantioenriched α-Hydroxy-α-perfluoroalkyl Esters
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This study has led to the development of a novel, highly efficient, 1,2-perfluoro-alkyl/-aryl migration process in reactions of hydrate of 1-perfluoro-alkyl/-aryl-1,2-diketones with alcohols, which are promoted by a Zn(II)/bisoxazoline and form α-perfluoro-alkyl/-aryl-substituted α-hydroxy esters. With (-)-8-phenylmenthol as the alcohol, the corresponding menthol esters are generated in high yields with excellent levels of diastereoselectivity. The mechanistic studies show that the benzilic ester-type rearrangement reaction takes place via an unusual 1,2-migration of electron-deficient trifluoromethyl group rather than the phenyl group. The overall process serves as a novel, efficient, and simple approach for the synthesis of highly enantioenriched, biologically relevant α-hydroxy-α-perfluoroalkyl carboxylic acid derivatives.
- Wang, Pan,Feng, Liang-Wen,Wang, Lijia,Li, Jun-Fang,Liao, Saihu,Tang, Yong
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p. 4626 - 4629
(2015/04/27)
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- Thioacids and thioacid salts for determining the enantiomeric excess of chiral compounds containing an electrophilic carbon center
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The invention provides novel chiral compounds including 2-methoxy-2-trifluoromethylphenylacetic thioacid useful to react with and analyze other chiral compounds that have an electrophilic chiral carbon center.
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Page/Page column 19-20
(2010/07/02)
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- Probing the parallel resolution of Mosher's acid using a combination of quasi-enantiomeric oxazolidin-2-ones
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Mosher's acid (2-methoxy-2-phenyl-2-trifluoromethylacetic acid) was resolved by parallel resolution of its corresponding pentafluorophenyl active ester using a quasi-enantiomeric combination of oxazolidin-2-ones.
- Chavda, Sameer,Coulbeck, Elliot,Dingjan, Marco,Eames, Jason,Motevalli, Majid
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p. 1274 - 1284
(2008/12/20)
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- Synthetic application of 3,3-dichloro-1, 1, 1-trifluoroacetone (DCTFA) and 3,3,3-trichloro-1, 1, 1-trifluoroacetone (TCTFA) for trifluorolactic acid derivatives
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Synthetic application of 3,3-dichloro-1,1,1-trifluoroacetone (DCTFA) and 3,3,3-trichloro-1,1,1-trifluoroacetone (TCTFA) for industrially important trifluorolactic acid derivatives is described. Trifluorolactic acid was obtained by hydrolysis of DCTFA unde
- Ishii, Akihiro,Kanai, Masatomi,Yasumoto, Manabu,Inomiya, Kenjin,Kuriyama, Yokusu,Katsuhara, Yutaka
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p. 567 - 571
(2007/10/03)
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- Enantioselective synthesis of arylmethoxyacetic acid derivatives
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The preparation of several arylmethoxyacetic acids by a sequence of asymmetric dihydroxylation and further oxidation of the resulting glycol with TEMPO/NaClO/NaClO2 is described. The scope and limitations of the reaction are discussed.
- Moreno-Dorado, F. Javier,Guerra, Francisco M.,Ortega, Maria J.,Zubia, Eva,Massanet, Guillermo M.
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p. 503 - 510
(2007/10/03)
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- An effective hydrolysis of crowded chiral esters
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Trifluoromethanesulfonic acid-coated silica in the absence of solvents is an effective reagent for hydrolysis of sterically crowded chiral esters giving chiral acids in good chemical and optical yield. On the other hand, the method was unsuitable for the
- Vávra, Jan,Streinz, Ludvík,Vodi?ka, Petr,Budě?ínsky, Milo?,Koutek, Bohumír
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p. 1886 - 1888
(2007/10/03)
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- Chiral discrimination of 2-arylalkanoic acids by (1S,2R)-1-aminoindan-2-ol through the formation of a consistent columnar supramolecular hydrogen-bond network
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Enantiopure cis-1-aminoindan-2-ol was selected as a basic resolving agent for racemic 2-arylalkanoic acids on the basis that its rigid cis-conformation would favor the formation of a supramolecular hydrogen-bonded column, in which chiral discrimination of the racemic carboxylate would occur. It was found that this amino alcohol possesses high resolving efficiency for a variety of racemic acids; also, X-ray crystallographic analyses of the diastereomeric salts showed that a columnar hydrogen-bond network is formed in both the less- and more-soluble diastereomeric salts, as we had expected. A detailed study on the stabilising interactions suggested that there are two that play an important role: (i) hydrogen bonding between the ammonium and hydroxy groups and the acid carboxylate, which determines the formation of the columnar network and (ii) CH...π, which influences the herringbone packing of the aromatic groups, implying that it also plays some role in chiral discrimination.
- Kinbara, Kazushi,Kobayashi, Yuka,Saigo, Kazuhiko
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p. 111 - 119
(2007/10/03)
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- Stereoselective Synthesis of Trifluoromethylated Compounds: Nucleophilic Addition of Formaldehyde N,N-Dialkylhydrazones to Trifluoromethyl Ketones
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The nucleophilic 1,2-addition of formaldehyde N,N-dialkylhydrazones 1, 2, and 7-10 to trifluoromethyl ketones 3a-e takes place in the absence of any catalyst or promoter to afford a series of α-hydroxy-α-trifluoromethylhydrazones (4, 5, and 11-14) in good-to-excellent yields. From the several reagents studied, optimal results were achieved using 1-(methyleneamino)pyrrolidine (2) for the synthesis of racemic adducts and (S)-l-(methyleneamino)-2-[1-(methoxy)diphenyl-methyl]-pyrrolidine (10) for the asymmetric version of the reaction. The resolving properties of the chiral auxiliary carried by 10 allowed an easy Chromatographic (flash) separation of any obtained diastereomeric mixture. Thus, a single operation rendered moderate-to-good amounts (42-75%) of optically pure adducts (S,S)-14 (de > 98%) by combining excellent chemical (82-92%) and moderate optical (51-81%) yields. Hydrazones 5 and (S,S)-14 were protected by benzylation [→ 16 and (SJS)-18] and then transformed into benzyl-protected α-trifluoromethyl cyanohydrins 21 by MMPP oxidative cleavage and into α-benzyloxy-a-trifluoromethyl aldehydes 22 by ozonolysis. Alternatively, adducts 5 and (S,S)-14 were methylated [→ 19 and (S,S)-20] and transformed into the corresponding α-methoxy-α-trifluoromethyl carboxylic acids 24 by successive ozonolysis and in situ oxidation (NaClO2, tBuOH, isobutene) of the crude a-methoxyaldehydes.
- Pareja, Carmen,Martin-Zamora, Eloisa,Fernandez, Rosario,Lassaletta, Jose M.
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p. 8846 - 8854
(2007/10/03)
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- A convenient preparation of (±)-α-methoxy-α-trifluoromethylphenylacetic acid (Mosher's acid)
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Mosher's acid can be prepared from PhC(O)CF3 via a vinylation, methylation, ozonolysis/oxidation sequence in >80% overall yield.
- Chong,Loewith
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p. 2145 - 2150
(2007/10/02)
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- Hydrolytic Resolution of Tertiary Acetylenic Acetate Esters With the Lipase from Candida Cylindracea
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The kinetic resolution of a series of tertiary acetylenic acetate esters using the lipase from Candida cylindracea has been explored.Compounds 6c and the trifluoromethyl acetate 6e have been resolved with high enantiomeric enrichment.Several other tertiary acetate esters carrying a CF3 group have been investigated which proved inert to enzymatic hydrolysis.From these results and published data, we are able to propose a predictive model for identifying the preferred enantiomer of secondary and tertiary trifluoromethyl acetate esters for this lipase.
- O'Hagan, David,Zaidi, Naveed A.
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p. 947 - 949
(2007/10/02)
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- MICROBIAL SYNTHESIS OF OPTICALLY PURE α-METHOXY-α-TRIFLUOROMETHYL-α-PHENYLACETIC ACID
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Preparation of optically pure α-methoxy-α-trifluoromethyl-α-phenylacetic acid via microbial asymmetric hydrolysis of cyanohydrin acetate as the key step is described.
- Ohta, Hiromichi,Miyame, Yoshitaka,Kimura, Yoichi
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p. 379 - 380
(2007/10/02)
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- A MODIFIED SYNTHESIS OF MOSHER'S ACID AND ITS USE IN A SENSITIVE STEREOISOMER ANALYSIS OF AMINO ACID DERIVATIVES
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A convenient and sensitive method for stereoisomer analysis of amino acid derivatives is described.It is based on the (19)F NMR-analysis of mixtures containing epimers of N-.-methoxy-.-trifluoromethyl-phenylacetyl alanine (MTPA).An improved procedure for the synthesis of MTPA is given.
- Hull, William E.,Seeholzer, Klaus,Baumeister, Marlies,Ugi, Ivar
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p. 547 - 552
(2007/10/02)
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- Determination of Enantiomeric Composition of Partly Racemized Carotenols
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Method for determining enantiomeric composition of various racemized carotenols by converting them into diastereomeric esters with subsequent analysis have been studied.Diastereomeric esters of (-)-camphanic acid with carotenols other than α-ketols could not be separated by HPLC.No separation was achieved for diastereomeric esters of methoxytrifluoromethylphenylacetic acid (MTPA). 1H NMR analysis in the presence of Eu(fod)3 of diastereomeric MTPA esters allowed quantitative determination of the enantiomeric composition of carotenols with 2-hydroxy-β- and 3-hydroxy-β-type end groups.
- Aareskjold, Kare,Liaaen-Jensen, Synnove
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p. 499 - 504
(2007/10/02)
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