- Investigation of the Organocatalytic Chlorination of 2-Phenylpropanal
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Results of an examination of the organocatalytic enantioselective α-chlorination of 2-phenylpropanal are described. Synthetic investigation including the screening of primary and secondary aminocatalysts, many different reaction conditions, and other α-br
- Mohr, Lisa-Marie,McCulley, Christina H.,Blom, Jakob,Lamhauge, Johannes N.,Anker J?rgensen, Karl
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supporting information
p. 17465 - 17475
(2021/10/25)
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- Trichloromethanesulfonyl chloride: A chlorinating reagent for aldehydes
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Trichloromethanesulfonyl chloride (CCl3SO2Cl), a commercially available reagent, has been found to perform efficiently in the α-chlorination of aldehydes, including its catalytic asymmetric version, under very mild reaction conditions. Under our reaction conditions, this compound outperforms typical chlorinating reagents for organic synthesis, facilitates workup and purification of the product, and minimizes the formation of toxic, chlorinated organic waste.
- Jimeno, Ciril,Cao, Lidong,Renaud, Philippe
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p. 1251 - 1255
(2016/02/19)
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- The Rabe amination after a century: Direct addition of N-heterocycles to carbonyl compounds
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A catalytic version of the Rabe electrophilic amination is presented. This kind of reaction was originally employed in 1918 in a key step for the conversion of quinotoxine to quinine. Ketones and α-substituted aldehydes give the corresponding α-aminated carbonyl compounds in moderate yield. α,α-Unsubstituted aldehydes give rise to amino ketones via a novel rearrangement.
- Scarpino Schietroma, Daniele M.,Monaco, Mattia R.,Bucalossi, Valerio,Walter, Philipp E.,Gentili, Patrizia,Bella, Marco
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scheme or table
p. 4692 - 4695
(2012/08/08)
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- Synthesis of 1,1-bisphosphono-2-aza-1,3-dienes, a new class of electron-deficient azadienes
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1,1-Bisphosphono-2-aza-1,3-dienes are formed by 1,4-dehydrohalogenation of the corresponding N-(bisphosphonomethyl)-α-haloimines in moderate to good yields. The precursors could be formed by condensation of bisphosphono-amines and the corresponding α-haloaldehydes.
- Masschelein, Kurt G.R.,Stevens, Christian V.
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p. 4336 - 4338
(2008/09/21)
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- Use of phenylselenium trichloride for simple and rapid preparation of α-phenylselanyl aldehydes and ketones
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α-Phenylselanyl aldehydes are prepared on a large scale by reaction of PhSeCl3 with the corresponding aldehydes in acetonitrile without isolation of the intermediate dichloro adducts. This method has been applied to α-phenylselanyl ketones deri
- Houllemare, Didier,Ponthieux, Sylvain,Outurquin, Francis,Paulmier, Claude
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p. 101 - 106
(2007/10/03)
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- α-Imino and α-oximino carbocations. A comparison with α-carbonyl and α-thiocarbonyl carbocations
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The σ+ values for the groups m-CH=N-t-Bu and p-CH=N-t-Bu have been determined to be 0.16 and 0.078, respectively. The CH=N-t-Bu group is therefore cation-destabilizing relative to hydrogen when placed in the meta position of a cumyl cation. Although the p-CH=N-t-Bu group is still cation-destabilizing, the effect is reduced by a competing resonance effect when the imino group is placed in the para position. However, when attached directly to a cationic center, this imino group enhances rates relative to α-H. This is interpreted in terms of a cation-stabilizing conjugative effect. The σ+ value of the p-oximino group, p-CH=NOCH3, is -0.03 and indicates that a cation-stabilizing conjugative effect can essentially offset the inductive effect of this electron-withdrawing substituent in a cumyl cation. However, when attached directly to a developing cationic center, this oximino group greatly enhances cation formation rates relative to hydrogen. This group is even more cation-stabilizing than the methyl group. Studies on systems of type ArCH(OMs)C(NOCH3)Ph, where the oximino group can be syn or anti to the developing cationic center, indicate the existence of isomeric α-oximino cations, with the anti cations forming faster than the syn cations. Computational studies at the MP2/6-31G** level support the idea of extensive conjugative stabilization of α-oximino cations. Despite extensive mesomeric stabilization of α-oximimo cations, the primary cation +CH2CH=NOCH3 cannot be solvolytically generated since nucleophilic solvent displacement processes dominate. Stabilities of a series of cations of type +CH2X, where X is a formal electron-withdrawing group, have been evaluated by ab initia methods. Isodesmic reactions indicate a stability order of α-CHNOCH3 ~ CH=CH2 > CHNHCH3 > CHS > CHO ~ H > CN > NO2.
- Creary, Xavier,Wang, You-Xiong,Jiang, Ziqi
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p. 3044 - 3053
(2007/10/02)
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- One-pot conversion of α-substituted arylacetaldehydes into α-dicarbonyl compounds
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α-dicarbonyl compounds 7-12 can be easily prepared by reaction of methylene chloride solutions of several α-substituted arylacetaldehydes 1-6 with a slight excess of tris-(o,p-dibromophenyl) ammoniumyl hexachloro antimonate A.
- Lopez, Luigi,Mele, Giuseppe,Nacci, Angelo,Troisi, Luigino
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p. 3897 - 3900
(2007/10/02)
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- Synthesis and Reactivity of 3-Oxazolines
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3-Oxazolines 1 have been prepared from α-hydroxy aldehydes, ammonia, water and a second oxo compound (aldehyde or ketone) in a one-pot reaction.Carboxylic acid chlorides add to the azomethine bond of 1 to yield 3-acyl-4-chlorooxazolidines 2. 4-Hydroxy and 4-alkoxyoxazolidines 3 are obtained from 2 upon treatment with aqueons sodium hydroxide or alkanol/triethyl amine, respectively.Some oxazolidines 3 are formed with high diastereoselectivity. Key Words: Oxazole, 2,5-dihydro- / Oxazolidine / Acyliminium ion
- Weber, Maya,Jakob, Juergen,Martens, Juergen
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- REACTIVITY OF α-ARYLSELENO-ALDEHYDES TOWARDS HALOGENS AND BENZENESELENENYL CHLORIDE
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Chlorination of α-seleno-aldehydes bearing an α-hydrogen gives selenium dichlorides which decompose into α-chloro α-seleno-aldehydes and α-chloroenal.Bromination, in all cases, and chlorination for the other α-seleno-aldehydes lead to the α-halogenoaldehydes.
- Paulmier, Claude,Outurquin, Francis,Plaquevent, Jean-Christophe
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p. 5893 - 5896
(2007/10/02)
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- ENANTIOSELECTIVE α-SELENENYLATION OF 2-PHENYLPROPANAL
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The parameters (media, temperature, structures of reactants) relative to the enantioselective α-selenenylation of 2-phenylpropanal with chiral areneselenenamides have been studied.Enantiomeric excesses as high as 60percent have been observed.Recrystallization yielded an α-seleno-aldehyde in an optically pure form.
- Paulmier, Claude,Outurquin, Francis,Plaquevent, Jean-Cristophe
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p. 5889 - 5892
(2007/10/02)
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- Anomer Controlled Substitution Reactions with Some N-Alkylpyridinium Compounds
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The results of semiempirical MNDO calculations on bond lengths, heats of formation, and net atomic charges of compounds 6, 7, and 8, which all contain an N-alkylpyridinium moiety (see Table 1), allow general trends to be recognized.These trends allow the prediction of important reactivity characteristics of this series of compounds and were the reason for the synthesis of compounds 9, 24, and 26 and for tests of their usefulness.Specifically, the C1-N2 bond length serves as a useful criterion for the reactivity with nucleophilic partners, especially in combination with thermodynamic data calculated from reactions (3) and (4) (Tables 3 and 4).In 7 and 8, this bond is very long as a consequence of an extreme anomeric effect.This observation is reflected in the (experimentally tested) property of the complexes 9 to split off the pyridine moiety.The Cl atom in 6a does not influence the C1-N2 bond length but it does activate the C1 atom toward nucleophilic attack and can itself function as the leaving group . - A remarkable example, both on the basis of the MNDO results (using the model compound 6i) and from the experimental viewpoint, was observed for the class of compounds 24a: The calculated C1-N2 bond length of 6i (1.563 Angstroem) could be classified as adequate for nucleophilic substitution of the pyridine moiety controlled by the anomeric effect on the basis of experimental tests.Whereas "normal" N-alkylpyridinium salts (e.g. the N-methylpyridinium cation, 6b) are hardly ever attacked in the C1 position, the preparative usefulness of this structural element can now be considerably increased by use of the anomeric effect.This is demonstrated by the synthesis of compounds 5, 9h, 17, and 22 from 9, 25a and 25b from 24a as well as 27a from 26a.
- Anders, Ernst,Markus, Fritz,Meske, Hermann,Tropsch, Juergen,Maas, Gerhard
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p. 735 - 746
(2007/10/02)
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- N-HALOAMIDINES.VI. REACTION OF N-CHLORO-N'-BENZENESULFONYLBENZAMIDINES WITH ENAMINES.
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The reaction between N-chloro-N'-benzenesulfonylbenzamidines and β,β-disubstituted enamines affords N-(benzenesulfonyl)-N'--benzamidines.When both β-substituents are methyl groups the open chain adducts have been isolated and characterized, whereas, when one of the two substituents is a phenyl group, they have been characterized only by PMR because of the easy cyclization to 1-benzenesulfonyl-4,5-dihydroimidazoles.
- Rossi, E.,Stradi, R.,Benedusi, A.
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p. 4785 - 4792
(2007/10/02)
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