2261-95-2Relevant academic research and scientific papers
Selective synthesis of trisubstituted pyrroles through the reactions of alkynyl Fischer carbene complexes with oxazolones
López, Julio,Velazco-Cabral, Iván,Rodríguez-DeLeón, Eloy,Villegas Gómez, Clarisa,Delgado, Francisco,Tamariz, Joaquín,Arrieta, Ana,Cossío, Fernando P.,Vázquez, Miguel A.
supporting information, p. 538 - 550 (2020/01/30)
An efficient and simple synthesis of novel trisubstituted 1H-pyrroles 4a-qvia 1,3-dipolar cycloaddition of Δ3-trifluoromethyloxazolones 2a-d with both chromium and tungsten alkynyl Fischer carbene complexes (1a-h) is described. An unexpected and unreported -CF3 group elimination process was observed in the pyrrole structure. Our experimental and theoretical data suggested that the metal fragment may be responsible for this phenomenon. The dipolar cycloaddition proceeded efficiently to produce a single regioisomer, which was unambiguously established through NMR and single-crystal X-ray diffraction studies. Nevertheless, the reaction of alkynyl carbenes bearing an α,β,γ,δ-unsaturated moiety with excess oxazolone 2a produced a polycyclic compound 6 speculatively formed through a cascade reaction involving 1,6-, 1,4- and 1,2-nucleophilic addition steps.
Cinchona Alkaloid Catalyzed Sulfa-Michael Addition Reactions Leading to Enantiopure β-Functionalized Cysteines
Breman, Arjen C.,Telderman, Suze E. M.,Van Santen, Roy P. M.,Scott, Jamie I.,Van Maarseveen, Jan H.,Ingemann, Steen,Hiemstra, Henk
, p. 10561 - 10574 (2015/11/18)
Sulfa-Michael additions to α,β-unsaturated N-acylated oxazolidin-2-ones and related α,β-unsaturated α-amino acid derivatives have been enantioselectively catalyzed by Cinchona alkaloids functionalized with a hydrogen bond donating group at the C6′ position. The series of Cinchona alkaloids includes known C6′ (thio)urea and sulfonamide derivatives and several novel species with a benzimidazole, squaramide or a benzamide group at the C6′ position. The sulfonamides were especially suited as bifunctional organocatalysts as they gave the products in very good diastereoselectivity and high enantioselectivity. In particular, the C6′ sulfonamides catalyzed the reaction with the α,β-unsaturated α-amino acid derivatives to afford the products in a diastereomeric ratio as good as 93:7, with the major isomer being formed in an ee of up to 99%. The products of the organocatalytic sulfa-Michael addition to α,β-unsaturated α-amino acid derivatives were subsequently converted in high yields to enantiopure β-functionalized cysteines suitable for native chemical ligation.
Enantioselective organocatalytic thiol addition to α,β- unsaturated α-amino acid derivatives
Breman, Arjenc.,Smits, Janm. M.,De Gelder, Rene,Van Maarseveen, Jan H.,Ingemann, Steen,Hiemstra, Henk
, p. 2195 - 2200 (2012/11/06)
A new class of Michael acceptors based on α,β-unsaturated amino acids has been prepared and applied in asymmetric organocatalysis. With the use of thiourea derivatives of cinchona alkaloid-derived catalysts, efficient addition of thiols to the dehydroamin
Eine neue Aminoazirin-Reaktion. Bildung von 3,6-Dihydropyrazin-2(1H)-onen
Hugener, Martin,Heimgartner, Heinz
, p. 172 - 179 (2007/10/02)
The reaction of 3-(dimethylamino)-2H-azirines 1 and 2-(trifluoromethyl)-1,3-oxazol-5(2H)-ones 5 in MeCN or THF at 50-80 deg leads to 5-(dimethylamino)-3,6-dihydropyrazin-2(1H)-ones 6 (Scheme 3).Reaction mechanisms for the formation of 6 are discussed: eit
Gas chromatographic and mass spectrometric characteristics of 2-trifluoromethyl-3-oxazol-5-ones. A potentially useful derivative for α-amino acids
Ferrito,Borg,Eagles,Fenwick
, p. 499 - 501 (2007/10/08)
The mass spectra of a number of 2-trifluoromethyl-3-oxazol-5-ones, prepared from protein amino acids, have been recorded. The compounds have been separated by gas chromatography using binary column techniques. Analysis of the mass spectra has identified m
