Search results for "Strecker"
showing 8 items of 18 documents
Enantioselective Synthesis of α-Quaternary Amino Acids by Alkylation of Deprotonated α-Aminonitriles.
2015
A series of α-quaternary arylglycines were prepared in high optical purity (up to 98% ee) by α-alkylation of deprotonated α-aminonitriles derived by the Strecker reaction from (4S,5S)-5-amino-2,2-dimethyl-4-phenyl-1,3-dioxane. The procedure includes only chromatographic purification of the final products and is devoid of chromatography or crystallization operations on intermediates to raise the optical purity.
ChemInform Abstract: Ring Expansion of 1,2,3,4-Tetrahydroisoquinolines to Dibenzo[c,f]azonines. An Unexpected [1,4]-Sigmatropic Rearrangement of Nitr…
2014
When the products of a Strecker reaction of 1,2,3,4-tetrahydroisoquinolines with aromatic aldehydes are quaternized with alkyl triflates and subsequently treated with base, a ring expansion to 6,7,8,13-tetrahydro-5H-dibenzo[c,f]azonine-5-carbonitriles takes place. The nine-membered cyclic products can be obtained in good yields (78–89%) in a process involving the [1,4]-sigmatropic rearrangement of a nitrile-stabilized ammonium ylide. The reaction sequence provides a new, simple, and efficient method for the synthesis of these unusual N-heterocycles.
ChemInform Abstract: Amino Acid Esters as Chiral Auxiliary Groups
2010
ChemInform Abstract: Enantioselective Synthesis of α-Quaternary Amino Acids by Alkylation of Deprotonated α-Aminonitriles.
2015
An α-alkylation of deprotonated α-amino nitriles, prepared from chiral phenyldioxanamine (I) by Strecker reaction, leads to α-quaternary arylglycines with high optical purity after hydrolysis and oxidative cleavage of the chiral auxiliary.
Lewis Acid-Catalyzed Stereoselection on Carbohydrate Templates
1989
The chirality and the complexing abilities of carbohydrates are utilized for chemical stereoselection in different reactions. In this sense, the carbohydrates are investigated as the chiral auxiliaries in alkylation reactions and in Michael additions of ester enolates. Furthermore, carbohydrates are demonstrated to be efficient chiral matrices in Lewis acid-catalyzed Diels-Alder reactions. They also effect stereoselection in a new synthesis of β-branched carboxylic acid derivatives. O-Acylated glycosylamines are shown to be potent chiral templates in the Strecker synthesis and in the Ugi four-component condensation to give α-amino acid derivatives in high yield and diastereoselectivity. In …
Ring Expansion of 1,2,3,4-Tetrahydroisoquinolines to Dibenzo[c,f]azonines. An Unexpected [1,4]-Sigmatropic Rearrangement of Nitrile-Stabilized Ammoni…
2014
When the products of a Strecker reaction of 1,2,3,4-tetrahydroisoquinolines with aromatic aldehydes are quaternized with alkyl triflates and subsequently treated with base, a ring expansion to 6,7,8,13-tetrahydro-5H-dibenzo[c,f]azonine-5-carbonitriles takes place. The nine-membered cyclic products can be obtained in good yields (78-89%) in a process involving the [1,4]-sigmatropic rearrangement of a nitrile-stabilized ammonium ylide. The reaction sequence provides a new, simple, and efficient method for the synthesis of these unusual N-heterocycles.
Facile Preparation of 3-Amino-4-(arylamino)-1H-isochromen-1-ones by a New Multicomponent Reaction
2005
Reactions between 2-formylbenzoic acid, various anilines and HCN result in the formation of 3-amino-4-(arylamino)-1H-isochromen-1-ones in high yield. The mechanism of this three-component condensation involves the intermediate formation of an α-aminonitrile and subsequent cyclization through nucleophilic attack of the ortho-carboxylate at the nitrile carbon. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
ChemInform Abstract: Reversal of Asymmetric Induction in Stereoselective Strecker Synthesis on Galactosyl Amine as the Chiral Matrix.
1989
Abstract The reversal of the direction of asymmetric induction in Lewis acid catalyzed Strecker synthesis using the 2,3,4,6-tetra-O-pivaloyl-β-D-galactopyranosyl amine 1 is described. In isopropanol or tetrahydrofuran 1 had given ( R )-diastereomers of the corresponding α-amino nitriles preferably. However, in chloroform in the presence of heterogeneous zinc chloride the same auxiliary alternatively leads to an excess of the ( S )-diastereomers.