RESUMO
A highly efficient N,P-ligated iridium complex is presented for the simple preparation of chiral tetrahydro-3-benzazepine motifs by catalytic asymmetric hydrogenation. Substrates bearing both 1-aryl and 1-alkyl substituents were smoothly converted to the corresponding hydrogenated product with excellent enantioselectivity (91-99% ee) and in isolated yield (92-99%). The synthetic value of this transformation was demonstrated by a gram-scale hydrogenation and application in the syntheses of trepipam and fenoldopam.
Assuntos
Carbamatos , Irídio , Catálise , Hidrogenação , EstereoisomerismoRESUMO
The transition metal-free intramolecular regioselective domino cyclization of N-Boc protected ynamides has been developed to provide the corresponding tetrahydroisoquinoline-oxazo-2(3H)-ones in moderate to good yields.
Assuntos
Acetatos/química , Alcinos/química , Amidas/química , Iodobenzenos/química , Isoquinolinas/síntese química , Oxazóis/síntese química , Boranos/química , Ciclização , Éter/química , Isoquinolinas/química , Estrutura Molecular , Oxazóis/química , EstereoisomerismoRESUMO
A Brønsted acid-catalyzed asymmetric Nazarov cyclization of acyclic α-alkoxy dienones has been developed. The reaction offers access to chiral cyclopentenones in a highly enantioselective manner. The reaction is complementary to our previously reported Brønsted acid-catalyzed electrocyclization reactions, which provided differently substituted optically active cyclopentenones with a fused tetrahydropyrane ring in good yields and with excellent enantioselectivities.
Assuntos
Ácidos/química , Álcoois/química , Catálise , Ciclização , Ciclopentanos/química , EstereoisomerismoRESUMO
The title compound, C(15)H(15)BrO(2), was synthesized by a Brønsted acid-catalysed domino electrocyclization-halogenation reaction. The five-membered ring is essentially planar (r.m.s. deviation 0.006â Å) and forms a dihedral angle of 72.7â (3)° with the attached phenyl ring. The six-membered heterocycle adopts a half-chair conformation. The crystal packing is stabilized by a C-Hâ¯O contact.
RESUMO
A highly efficient Brønsted acid catalyzed enantioselective Nazarov cyclization-bromination reaction has been developed. The protocol gives access to highly functionalized trans-4,5-substituted 5-bromocyclopentenone derivatives in good yields and with excellent enantioselectivities.
RESUMO
Recently, chiral highly acidic Brønsted acids have emerged as powerful catalysts for enantioselective C-C and C-X bond-forming reactions. Their strong acidity renders them valuable tools for the activation of imines, carbonyl compounds, and other weakly basic substrates. As a result, new perspectives are opened and highly stereoselective transformations based on the concept of chiral contact-ion-pair catalysis can be realized. This Minireview gives an overview of the design and application of these new organocatalysts and presents recent results in this rapidly growing field.
RESUMO
The design of biologically inspired, multi-component cascade reactions enables the targeted synthesis of assorted structurally complex products. Similar to regulation in cells the reaction path is controlled by the substrate concentration and complex enantiopure products with high structural diversity are provided.
Assuntos
Materiais Biomiméticos/síntese química , Biomimética/métodos , Catálise , EstereoisomerismoRESUMO
Recently, 1,1'-bi-2-naphthol (BINOL)-based N-triflylphosphoramides emerged as a new class of potent Brønsted acid catalysts. In this paper we describe the efficient synthesis of various BINOL-based N-triflylphosphoramides and their calcium salts. Furthermore, X-ray crystal structure analysis combined with energy-dispersive X-ray spectroscopy (EDX) measurements confirmed that the synthesised chiral N-triflylphosphoramides are highly acidic metal-free catalysts.
RESUMO
The bromine-magnesium exchange reactions of arylthiobromodifluoromethanes with Grignard reagents have been studied. Upon trapping with electrophiles, alkyl aryl sulfides and ketenedithioacetals are obtained. The reaction is proposed to occur via novel alpha-arylsulfanyl-alpha-fluoro carbenoids. The first examples of arylthiomethane multipole synthons are also reported. [reaction: see text]