- Enantioselective Synthesis of Quaternary Δ4- and Δ5-Dehydroprolines Based on a Two-Step Formal [3+2] Cycloaddition of α-Aryl and α-Alkyl Isocyano(thio)acetates with Vinyl Ketones
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A divergent synthesis of optically active quaternary Δ4- and Δ5-dehydro prolines is developed based on the first catalytic enantioselective conjugate addition of α-substituted isocyano(thio)acetates to vinyl ketones that is general for both α-aryl and α-alkyl isocyano(thio)acetates. The new tetrasubstituted C?N stereocenter is formed without the need of any metal salt due to a bifunctional tertiary amine/squaramide catalyst, featuring a bulky polyaryl sidearm and an unusually short squaramide diamide H???H interatomic distance in the solid state.
- Odriozola, Amaiur,Oiarbide, Mikel,Palomo, Claudio
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supporting information
p. 12758 - 12762
(2017/09/25)
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- Amidation reactions from the direct coupling of metal carboxylate salts with amines
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A general method for the synthesis of amides involving the direct coupling of alkali metal carboxylate salts with amines is described. Amidation of a wide variety of carboxylate salts with either free amines or their ammonium hydrochloride salts can be achieved using HBTU as a coupling agent in combination with Huenig's base. The reaction is highly efficient and is generally complete in as little as 1-2 h, giving the products in good to excellent yields. The protocol is valuable for the coupling of carboxylates for which the corresponding carboxylic acids or acyl chlorides are unstable, less conveniently manipulated/isolated, or are not commercially available. For example, the coupling of amines and α-amino acids with lithium 5-bromo-1H-pyrrole-2-carboxylate, whose corresponding acid that is prone to decarboxylation, allowed for the synthesis of 5-bromo-1H-pyrrole-2-carboxamides, which are analogues of the pyrrole-2-aminoimidazole marine alkaloids. The protocol can be combined with other reactions in a sequenced fashion, as exemplified by the synthesis of acetylenic amides, in a one-pot procedure, via the coupling of a lithium carboxylate salt formed initially by the addition of carbon dioxide to a lithiated terminal alkyne.
- Goodreid, Jordan D.,Duspara, Petar A.,Bosch, Caroline,Batey, Robert A.
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p. 943 - 954
(2014/03/21)
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- Enantioselective synthesis of 1,2,4-triazolines by chiral iron(ii)-complex catalyzed cyclization of α-isocyano esters and azodicarboxylates
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Enantioselective cyclization of α-isocyano esters with azodicarboxylates catalyzed by FeII-N,N′-dioxide complexes has been developed. Under mild conditions, a variety of 1,2,4-triazoline derivatives was obtained in high yields and enantioselectivities.
- Wang, Min,Liu, Xiaohua,He, Peng,Lin, Lili,Feng, Xiaoming
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p. 2572 - 2574
(2013/04/10)
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- Synthesis of 1,2,4-triazolines: Base-catalyzed hydrazination/cyclization cascade of α-isocyano esters and amides
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A convenient, efficient synthesis of 1,2,4-triazolines from α-isocyano esters/amides and azodicarboxylates is presented. The developed reaction cascade is based on a base-catalyzed hydrazination-type reaction followed by a subsequent cyclization providing
- Monge, David,Jensen, Kim L.,Marin, Irene,Jorgensen, Karl Anker
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supporting information; experimental part
p. 328 - 331
(2011/03/23)
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- Versatile selective α-carboxylic acid esterification of N-protected amino acids and peptides by alcalase
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Under continuous removal of water, the industrial protease Alcalase allows selective synthesis of α-carboxylic acid methyl, ethyl, benzyl, allyl, 2-(trimethylsilyl)ethyl, and tert-butyl esters of amino acids and peptides under mild conditions in very high
- Nuijens, Timo,Cusan, Claudia,Kruijtzer, John A. W.,Rijkers, Dirk T. S.,Liskamp, Rob M. J.,Quaedflieg, Peter J. L. M.
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scheme or table
p. 809 - 814
(2009/07/11)
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- A mild method for formylating amino esters without using any formulating agent
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A simple and mild method for the N-formylation of α-amino esters is described via an intermediate oxaziridine. This procedure avoids the necessity of specific formylating agents and yields the N-formyl species in high yield and without racemization.
- Giard, Thierry,Bénard, Didier,Plaquevent, Jean-Christophe
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p. 297 - 300
(2007/10/03)
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- A simple and convenient synthesis of N-formyl amino acid esters under mild conditions
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A variety of amino acid ester hydrochlorides react with cyanomethyl formate at room temperature to give the N-formyl amino acid esters in good yields and without racemization.
- Duczek,Deutsch,Vieth,Niclas
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- A new formylating reagent: N-(diethylcarbamoyl)-N-methoxyformamide
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A simple and efficient method for the direct chemoselective formylation of primary amines in the presence of alcohols or secondary amines using a new reagent, N-(diethylcarbamoyl)-N-methoxyformamide is described.
- Akikusa,Mitsui,Sakamoto,Kikugawa
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p. 1058 - 1060
(2007/10/02)
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- Preparation of N-Formylpyridones - Selective Esterification of Primary, Secondary and Tertiary Alcohols with N-Acylpyridones
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Formylation of monohydroxypyridines 1-3 with formic acid in the presence of dicyclohexylcarbodiimide in dichloromethylene yields N-formyl-4- (4), N-formyl-2-pyridone (5), and 3-(formyloxy)pyridine (6), resp.These acylpyridones react with prim., sec., and tert. alcohols with selectivity decreasing reactivity to give the formyl esters 7.
- Effenberger, Franz,Keil, Michael,Bessey, Eberhard
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p. 2110 - 2119
(2007/10/02)
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