- Enantioselective α-Chlorination Reactions of in Situ Generated C1 Ammonium Enolates under Base-Free Conditions
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The asymmetric α-chlorination of activated aryl acetic acid esters can be carried out with high levels of enantioselectivities utilizing commercially available isothiourea catalysts under base-free conditions. The reaction, which proceeds via the in situ formation of chiral C1 ammonium enolates, is best carried out under cryogenic conditions combined with a direct trapping of the activated α-chlorinated ester derivative to prevent epimerization, thus allowing for enantioselectivities of up to e.r. 99:1.
- Stockhammer, Lotte,Weinzierl, David,B?gl, Thomas,Waser, Mario
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p. 6143 - 6147
(2021/08/18)
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- Efficient α-chlorination of carbonyl containing compounds under basic conditions using methyl chlorosulfate
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An efficient method for the α-chlorination of ketones under basic conditions is described using methyl chlorosulfate. Its applicability for the chlorination of other functional groups has also been studied and it is equally useful for the synthesis of α-chloroesters and amides. Methyl chlorosulfate is described for the first time as a positive chlorine source. Some aldol reactions which occur during the chlorination of some substrates are also reported.
- Silva, Saúl,Maycock, Christopher D.
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supporting information
p. 1233 - 1238
(2018/02/27)
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- Iodobenzene Dichloride in the Esterification and Amidation of Carboxylic Acids: In-Situ Synthesis of Ph3PCl2
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A novel, in-situ synthesis of dichlorotriphenylphosphorane (Ph3PCl2) is accomplished upon combining PPh3and the easily prepared hypervalent iodine reagent iodobenzene dichloride (PhICl2). The phosphorane is selectively generated in the presence of carboxylic acid or alcohol residues to rapidly produce acyl chlorides and alkyl chlorides in high yields. Addition of EtOH, PhOH, BnOH, Et2NH or CH2N2results in the direct synthesis of esters, amides and diazo ketones from carboxylic acids.
- Carle, Myriam S.,Shimokura, Grace K.,Murphy, Graham K.
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supporting information
p. 3930 - 3933
(2016/08/24)
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- Aromatic cation activation: Nucleophilic substitution of alcohols and carboxylic acids
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A new method for the nucleophilic substitution of alcohols and carboxylic acids using aromatic tropylium cation activation has been developed. This article reports the use of chloro tropylium chloride for the rapid generation of alkyl halides and acyl chlorides under very mild reaction conditions. It demonstrates, for the first time, the synthetic potential of tropylium cations in promoting chemical transformations.
- Nguyen, Thanh V.,Bekensir, Alp
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p. 1720 - 1723
(2014/04/17)
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- SUBSTITUTED PHENYLLUREAS AND PHENYLAMIDES AS VANILLOID RECEPTOR LIGANDS
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The invention relates to substituted phenylureas and phenylamides of formula (I), to processes for the preparation thereof, to pharmaceutical compositions containing these compounds and also to the use of these compounds for preparing pharmaceutical compositions.
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Page/Page column 108; 109
(2010/11/18)
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- Vanilloid receptor ligands, pharmaceutical compositions containing them, process for making them and use thereof for treating pain and other conditions
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Compounds corresponding to formula I: which act as vanilloid receptor ligands, pharmaceutical compositions containing such compounds, a process for the producing such compounds, and the use thereof to treat or inhibit pain and/or various other disorders or conditions.
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Page/Page column 32-33
(2008/12/08)
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- Enzymatic hydrolysis and selective racemisation reactions of α-chloro esters
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The kinetic resolution of α-chloro esters was effected with good selectivity using CLEC (Cross-Linked Enzyme Crystals) enzymes. The selective racemisation of α-chloro esters in the presence of α-chloro acids enabled a successful dynamic kinetic resolution reaction to be performed.
- Haughton, Louise,Williams, Jonathan M. J.
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p. 943 - 946
(2007/10/03)
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- Effect of fluorine substitution of α-and β-hydrogen atoms in ethyl phenylacetate and phenylpropionate on their stereoselective hydrolysis by cultured cancer cells
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(±)-Ethyl 2-fluoro-2-phenylacetate was stereoselectively hydrolyzed by cultured cells of several rat cancer cell lines to give the carboxylic acid rich in the R enantiomer. The stereoselectivity increased for (±)-ethyl 2-fluoro-2-phenylpropionate (2b) with all present cell lines and for (±)-ethyl 2-phenyl-3,3,3-trifluoropropionate (3b) with rat hepatoma McA-RH7777 cell line. The stereoselectivity was different for the different cell lines, as McA-RH7777 cells preferred (R)-2b in contrast with the preference towards (S)-2b by other cells such as ras oncogene-transformed rat liver Anr4 cells. These stereoselectivities were different from those for non-fluorinated (±)-ethyl 2-phenylpropionate. Thus fluorine atoms are recognized by ester hydrolases of cancer cells, and fluorine substitution on the acyl group will be useful for making ester-type anticancer prodrugs more specific to cancer cells.
- Yamazaki, Yoshimitsu,Yusa, Shiro,Kageyama, Yu-Ichi,Tsue, Hirohito,Hirao, Ken-Ichi,Okuno, Hiroaki
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p. 167 - 171
(2007/10/03)
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- Synthesis of 4-oxo-2-azetidineacetic acids by means of radical cyclization of N-vinylic α-bromo amides
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Bu2SnH-mediated radical cyclization of α-bromo amide 8, bearing phenyl and phenylthio substituents at the terminus of the N-vinylic bond, proceeded in a 4-exo-trig manner to give β-lactam 9. Ruthenium tetroxide oxidation of the phenyl group incorporated into the product 9 provided a new synthesis of 4-oxo-2-azetidineacetic acid 13, a useful intermediate for (±)-PS-5. Chiral 4-oxo-2-azetidineacetic acids 23 and 36, key intermediates for the synthesis of (+)-PS-5 and (+)-thienamycin, respectively, were also obtained through the asymmetric radical cyclization of N-vinylic α-bromo amides having chiral auxillaries at the side-chain.
- Ishibashi, Hiroyuki,Kodama, Kazuya,Kameoka, Chisato,Kawanami, Hirotaka,Ikeda, Masazumi
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p. 13867 - 13880
(2007/10/03)
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