RESUMO
A highly chemoselective reaction between 5-aminoisoxazoles and α-diazocarbonyl compounds has been described. Both Wolff rearrangement and N-H insertion products can be obtained selectively by the judicious choice of reaction conditions. In the case of the Wolff rearrangement reactions, the N-isoxazole amides are accessed as the sole products under thermal conditions. On the other hand, α-amino acid derivatives of N-isoxazolescan be obtained through N-H insertion reactions in the presence of catalytic Rh2(Oct)4. Both reactions proceed under mild reaction conditions and feature a broad substrate scope.
RESUMO
An efficient RhII -catalyzed synthesis of functionalized α-vinyl aldehydes with high E/Z stereoselectivity was developed. The reaction mediates the cyclopropanation of enaminones with vinyl carbenoids that are generated from cyclopropenes inâ situ to give the aminocyclopropane intermediates. Selective C-C bond cleavage of the cyclopropane intermediates leads to formation of α-vinyl aldehyde derivatives with high E/Z selectivity. This method proceeds at room temperature under very mild reaction conditions and works with a broad substrate scope.
RESUMO
An organocatalytic formal [4 + 2] cycloaddition reaction has been realized that permits rapid access to a wide range of bicyclo[2.2.1]heptane-1-carboxylates in a highly enantioselective manner from simple starting materials under mild and operationally simple conditions.
RESUMO
The asymmetric total syntheses of hedyosumin E aglycon, 7,10-epoxyhedyosminolide and ent-zedolactone A were realized, with the first two being achieved for the first time.
Assuntos
4-Butirolactona/análogos & derivados , Sesquiterpenos de Guaiano/síntese química , 4-Butirolactona/síntese química , 4-Butirolactona/química , Catálise , Cristalografia por Raios X , Reação de Cicloadição , Modelos Moleculares , Sesquiterpenos de Guaiano/química , EstereoisomerismoRESUMO
In the title compound, C(21)H(28)N(2)O(4), the dihydro-pyridine ring adopts a flattened boat conformation. The mean plane of the dihydro-pyridine ring and the attached benzene ring form a dihedral angle of 85.1â (1)â Å. One of two ethyl fragments is disordered between two conformations in a 0.67â (4):0.33â (4) ratio. In the crystal structure, mol-ecules related by translation along the a axis are linked into chains via inter-molecular N-Hâ¯O hydrogen bonds.
RESUMO
An efficient copper-catalyzed direct C(sp2)-H/C(sp3)-H coupling reaction of aza-aromatic rings with fluoroalcohols is developed. A variety of useful building blocks including hydroxyfluoroalkylated aniline, pyrrole, and indole derivatives bearing a quaternary carbon center could be constructed with high regioselectivity and good to excellent yields under very mild reaction conditions. The reaction is believed to undergo a fluoroalcohol oxidation and to follow an electronic addition reaction pathway.
RESUMO
A mild rhodium catalytic system has been developed to synthesize vinylcyclopropa[b]indolines through cyclopropanation of indoles with vinyl carbenoids generated from ring opening of cyclopropenes in situ. By employing a Rh-migration strategy, the products can be obtained with good to excellent E:Z ratios (≤99:1) and complete diastereoselectivity (≤99:1). This method is easy, has a low catalyst loading, and works for a broad range of functionalities.
RESUMO
2H-Azirine-2-caboxamides have been designed to perform as a new type of bifunctional thiol linker under very mild reaction conditions. The cleavage of a C-N double bond of 2H-azirine furnishes an amino amide functional group in situ through a thiol addition and ring-opening process. It works with a broad scope of thiols and 2H-azirines in the absence of any catalysts at room temperature. Cysteine-containing peptides have also been demonstrated to work efficiently in a completely water solution.
Assuntos
Azirinas/química , Cisteína/química , Catálise , Estrutura Molecular , TecnologiaRESUMO
A straightforward strategy for synthesis of highly functionalized trifluoromethyl 2H-furans is described. The copper catalyzed method relies on a cascade cyclic reaction between enaminones and N-tosylhydrazones. This method allows the synthesis of 2-amino-3-trifluoromethyl-substituted 2H-furan derivatives carrying a quaternary stereogenic center as single diastereomers. The proposed reaction mechanism involves an amino-cyclopropane intermediate formed in the cyclopropanation of enaminones. The developed method tolerates a broad spectrum of functionalities, and the obtained 2H-furan derivatives are useful synthetic intermediates for preparing other trifluoromethyl-substituted compounds.
RESUMO
A one-pot reaction to synthesize functionalized 2 H-azirines through visible-light-mediated ring contraction and olefin metathesis of isoxazoles is described. Hoveyda-Grubbs II catalyst was found to function as a photocatalyst for these transformations, allowing these processes to be carried out in a one-pot manner. This study offers a new entry for the application of Grubbs catalysts as efficient photocatalysts and the possibilities of carrying out other photoreactions and olefin metathesis in a one-pot process.
RESUMO
An expedient [5 + 1] annulation method via Rh(III)-catalyzed C-H bond functionalization of enaminones to synthesize polyaromatic rings is described. The reaction tolerates a broad range of functional groups and offers a new entry to construct polycyclic aromatic compounds with amino and formyl substituents. A possible reaction mechanism was proposed based on the results obtained from isotope labeling experiments.
RESUMO
The first and asymmetric total synthesis of hedyosumins A, B, and C was accomplished in 13-14 steps from simple starting materials. The essential tools that allow us to access the tetracyclic skeleton include an organocatalytic [4 + 3] cycloaddition reaction, an intramolecular aldol condensation, and an intramolecular carboxymercuration/demercuration enabled lactonization. A CBS-catalyzed asymmetric reduction was employed to boost the ee of the synthetic natural products to an excellent level. This synthesis established the absolute configurations of hedyosumins A, B, and C.