4026-18-0Relevant articles and documents
2-Bromo-6-isocyanopyridine as a Universal Convertible Isocyanide for Multicomponent Chemistry
Van Der Heijden, Gydo,Jong,Ruijter, Eelco,Orru, Romano V. A.
supporting information, p. 984 - 987 (2016/03/15)
The development of 2-isocyanopyridines as novel convertible isocyanides for multicomponent chemistry is reported. Comparison of 12 representatives of this class revealed 2-bromo-6-isocyanopyridine as the optimal reagent in terms of stability and synthetic efficiency. It combines sufficient nucleophilicity with good leaving group capacity of the resulting amide moiety under both basic and acidic conditions. To demonstrate the practical utility of this reagent, an efficient two-step synthesis of the potent opioid carfentanil is presented.
Chiral propargylic cations as intermediates in SN1-type reactions: Substitution pattern, nuclear magnetic resonance studies, and origin of the diastereoselectivity
Nitsch, Dominik,Huber, Stefan M.,Poethig, Alexander,Narayanan, Arjun,Olah, George A.,Prakash, G. K. Surya,Bach, Thorsten
supporting information, p. 2851 - 2857 (2014/03/21)
Nine propargylic acetates, bearing a stereogenic center (-C*HXR 2) adjacent to the electrophilic carbon atom, were prepared and subjected to SN1-type substitution reactions with various silyl nucleophiles employing bismuth trifluoromethanesulfonate [Bi(OTf)3] as the Lewis acid. The diastereoselectivity of the reactions was high when the alkyl group R2 was tertiary (tert-butyl), irrespective of the substituent X. Products were formed consistently with a diastereomeric ratio larger than 95:5 in favor of the anti-diastereoisomer. If the alkyl substitutent R2 was secondary, the diastereoselectivity decreased to 80:20. The reaction was shown to proceed stereoconvergently, and the relative product configuration was elucidated. The reaction outcome is explained by invoking a chiral propargylic cation as an intermediate, which is preferentially attacked by the nucleophile from one of its two diastereotopic faces. Density functional theory (DFT) calculations suggest a preferred conformation in which the group R2 is almost perpendicular to the plane defined by the three substituents at the cationic center, with the nucleophile approaching the electrophilic center opposite to R2. Transition states calculated for the reaction of allyltrimethylsilane with two representative cations support this hypothesis. Tertiary propargylic cations with a stereogenic center (-C* HXR2) in the α position were generated by ionization of the respective alcohol precursors with FSO3H in SO2ClF at -80 C. Nuclear magnetic resonance (NMR) spectra were obtained for five cations, and the chemical shifts could be unambiguously assigned. The preferred conformation of the cations as extracted from nuclear Overhauser experiments is in line with the preferred conformation responsible for the reaction of the secondary propargylic cations.
A stable, convertible isonitrile as a formic acid carbanion [ -COOH] equivalent and its application in multicomponent reactions
Kreye, Oliver,Westermann, Bernhard,Wessjohann, Ludger A.
, p. 3188 - 3192 (2008/09/20)
The application of 2-(2,2-dimethoxyethyl) phenyl isonitrile in Ugi, Passerini, and Ugi-Smiles reactions is described. The simple transformation to highly activated indolyl amides allows functional-group conversion of the isonitrile moiety into a variety of carboxylic acid derivatives, overall acting as a neutral, nucleophilic COOH equivalent. Georg Thieme Verlag Stuttgart.
PROCESS FOR PRODUCTION OF OPTICALLY ACTIVE 2-HALOGENO- CARBOXYLIC ACIDS
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Page 8, (2008/06/13)
The invention provides processes for producing efficiently optically active 2-halogenocarboxylic acids useful in the preparation of drugs or the like and salts thereof with amines. Specifically, an optically active 2-halogenocarboxylic acid is produced by halogenating an optically active amino acid in water in the presence of a hydrophobic organic solvent and nitrous acid with the configuration retained and with the racemization inhibited through the removal of 2-hydroxy- bromocarboxylic acid formed as a by-product; the obtained optically active 2-halogenocarboxylic acid is transferred to an aqueous phase by converting it into a salt thereof with a base, followed by the removal of the organic phase; and the optically active 2-halogenocarboxylic acid is transferred again to an organic solvent phase, followed by the removal of the aqueous phase, whereby an optically active 2-halogenocarboxylic acid is obtained through the removal of a halogen component. Further, a high-quality salt of an optically active 2-halogenocarboxylic acid with an amine can be obtained by a crystallization method wherein the amine is added over the period of 1/2 hour or longer either continuously or in portions and/or wherein the crystallization solvent consists of a hydrophobic organic solvent and a hydrophilic organic solvent.
pH-Dependent Chemoselective Synthesis of α-Amino Acids. Reductive Amination of α-Keto Acids with Ammonia Catalyzed by Acid-Stable Iridium Hydride Complexes in Water
Ogo, Seiji,Uehara, Keiji,Abura, Tsutomu,Fukuzumi, Shunichi
, p. 3020 - 3021 (2007/10/03)
An acid-stable hydride complex [Cp*IrIII(bpy)H]+ {1, Cp* = η5-C5Me5, bpy = 2,2′-bipyridine} serves as the active catalyst for the highly chemoselective synthesis of α-amino acids by reductive aminatio
Synthetic methods for aplidine and new antitumoral derivatives, methods of making and using them
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, (2008/06/13)
The invention provides aplidine derivatives and synthetic methods.
New cyclic depsipeptide antibiotics, clavariopsins A and B, produced by an aquatic hyphomycetes, Clavariopsis aquatica: 2. Structure analysis
Suzuki,Ojika,Sakagai,Kaida,Fudou,Kameyama
, p. 22 - 28 (2007/10/03)
The structures of new cyclic decadepsipeptides, clavariopsins A and B, were determined to be cyclo[-(R)-2-hydroxyisovaleryl-L-pipecolyl-L-MeVal- L-Val-L-MeAsp-L-Melle-L-Melle-Gly-L-MeVal-L-Tyr(OMe)-] and cyclo[-(R)-2- hydroxyisovaleryl-L-pipecoly-L-Val-L-Val-L-MeAsp-L-Melle-L-Melle-Gly-L- MeVal-L-Tyr(OMe)-], respectively, by spectroscopic analyses, especially using 2D NMR techniques. The absolute stereochemistry was elucidated by the advanced Marfey's method and chiral HPLC analysis.
An efficient α-hydroxylation of carbonyls using the HOF·CH3CN complex
Dayan, Sharon,Bareket, Yifat,Rozen, Shlomo
, p. 3657 - 3664 (2007/10/03)
The complex HOF·CH3CN, made directly from fluorine and aqueous acetonitrile, was used for α-hydroxylation of various ketones, esters and acids via their trimethyl silyl enol ethers. The reaction is usually complete in a few minutes at room temperature or below and has high yields.
Reaction of carboxylic acids with diethyl phosphorocyanidate; a novel synthesis of homologated α-hydroxycarboxylic acids from carboxylic acids
Mizuno, Masanori,Shioiri, Takayuki
, p. 9209 - 9210 (2007/10/03)
Carboxylic acids react with 2 equivalents of diethyl phosphorocyanidate in the presence of triethylamine to give dicyanophosphates in good yields; these dicyanophosphates can be hydrolyzed easily to give homologated α- hydroxycarboxylic acids.
Enantioselectivity of Pseudomonas cepacia lipase for the acetylation of 2-hydroxy carboxylic acid esters+
Sundholm, Oskari,Kanerva, Liisa T.
, p. 625 - 640 (2007/10/03)
Structurally different ethyl or methyl 2-hydroxy carboxylates were resolved by Pseudomonas cepacia lipase-catalysed acetylations with vinyl acetate in diethylether. One type of the alcoholic substrates (2-hydroxy-2-arylacetates and 2-hydroxy-3-arylpropinates) contained a HO-group at the stereocentre. These compounds were resolved with high enantioselectivity (ee 91 → 99) at ca. 50% conversion. The other alcoholic substrates ((threo-2-hydroxy-3-methylbutyrate and threo- or erythro-2-hydroxy-3-aryl-3-arylthio(or aryloxy)propionates) with two stereocentres generally resulted in enantiopure products and the reactions stopped at 50 % conversion.
