RESUMO
The combination of visible light catalysis and Ni catalysis has enabled the synthesis of indolyl phenyl diketones through the cyclization/oxidation process of ynones. This reaction proceeded under mild and base-free conditions and showed a broad scope and feasibility for gram-scale synthesis. Several natural products and biologically interesting molecules could be readily postfunctionalized by this method.
RESUMO
The first synthesis of unnatural ß2,3,3-amino acids with a spirocyclic backbone by one-pot protocol has been presented. This reaction features wide functional group tolerance and feasibility of post-functionalization of natural products and biologically important molecules. Novel dipeptide and tripeptide structures were assembled using this newly developed ß2,3,3-amino acid in high efficiency. The combination of C-H activation and C-C cleavage for the synthesis of ß-amino acids would trigger more promising synthetic routes for this compound.
RESUMO
Using dichloromethane (DCM) as the C1 feedstock, the first Pd(0)-catalyzed synthesis of aryl-methylene ether motifs from hydrobenzoxazoles (hydrothiazoles) has been reported. This protocol has exhibited an ample substrate scope (38 examples) and wide functional group tolerance. Aryl-methylene ether adducts have been successfully engaged in coupling with isocyanate to provide bis-iminoisoindolinones. In this reaction, DCM has served as a twofold electrophile for reaction with hydrobenzoxazoles via double C-Cl bond cleavage.
RESUMO
The unprecedented Pd-catalyzed (ethoxycarbonyl)difluoromethylthiolation reaction of various unsaturated derivatives was studied. In the presence of the (ethoxycarbonyl)difluoromethylsulfenamide reagent I and under mild reaction conditions (60 °C), both 2-(hetero)aryl and 2-(α-aryl-vinyl)pyridine derivatives were smoothly functionalized with this methodology (37 examples, up to 87 % yield). Moreover, the synthetic interest of this fluorinated moiety was further showcased by its conversion into various original fluorinated residues. Finally, a plausible mechanism for this transformation was suggested.
Assuntos
Paládio , Paládio/química , CatáliseRESUMO
An unexpected cleavage of the Csp3-CF3 bond of CF3-hydrobenzoxazoles has been disclosed, affording a range of 2-aryl benzoxazoles under metal-free and redox-neutral conditions. This transformation has demonstrated broad substrate scope and good compatibility of functional groups. 2-Aryl benzothiazole and 2-aryl benzoimidazole could be smoothly assembled in the same manner. On the basis of preliminary mechanistic studies, base initiated and aromatization driven ß-carbon elimination was considered to be the key step for the formation of 2. This reaction offers an alternative, facile, and sustainable route to access important 2-aryl benzoxazole motifs.
Assuntos
Benzoxazóis , Paládio , Carbono , Catálise , OxirreduçãoRESUMO
An unprecedented 1,3-dipole cycloaddition between acyclic CF3-ketimines and N-benzyl azomethine ylide has been allowed by tungsten catalysis, furnishing a range of novel imidazolidines bearing a trifluoromethylated tetrasubstituted carbon center. This reaction appears as one of rare examples that challenging acyclic CF3-ketimines have been engaged in 1,3-cycloaddition reactions. The capability for gram-scale synthesis and variant derivatizations of cycloaddition adducts illustrates the synthetic potential of this approach. This protocol provides a facile access to a rapidly enlarging pool of motifs with a trifluoromethylated fully substituted carbon.
RESUMO
The [3+2] annulation of trifluoromethylated ketimines with acrylates has been enabled by rhenium-catalyzed C-H activation, delivering a variety of ß-CF3 ß-amino esters. The reaction has exhibited broad substrate generality regarding aromatic CF3-ketimines and acrylates, the ability for gram scale synthesis, and facile derivation of the annulation products. The transformation is one of the few examples in which challenging sp2 C-H bonds of CF3-ketimines have been functionalized. The rapid assembly of biologically important fluorinated ß-amino esters by this strategy will benefit the related studies and inspire a new approach for fluorinated motif synthesis.
RESUMO
Transition metal catalyzed [3 + 2] annulation of imines with double bonds via directed C-H activation offers a direct access to amino cyclic motifs. However, owing to weak coordination and steric hindrance, trifluoromethylated ketimines have been an unaddressed challenge for TM-catalyzed annulations. Here, a rhenium-catalyzed [3 + 2] annulation of trifluoromethylated ketimines with isocyanates via C(sp2)-H activation has been disclosed. This approach provides an efficient platform for rapid access to a privileged library of CF3-containing iminoisoindolinones and polyamides by utilizing challenging CF3-ketimines as the annulation component. The capability of gram scale synthesis, the post-functionalization of the cyclization adduct, the derivation of complex natural molecules and the facile synthesis of polyamides highlight a diversity of synthetic potential of the current methodology.
RESUMO
The intermolecular deacylative coupling of unstrained ynones via C-C bond activation was accomplished by a CuCl-bpy system under mild reaction conditions. This protocol features facile cleavage of the C-C bond at room temperature, broad substrate scope, and efficient construction of important symmetric and unsymmetrical 1,3-diyne adducts through homo or cross coupling of ynones, respectively. The preliminary mechanistic investigations indicated that an acyl copper(III) complex is likely involved in this process.
RESUMO
A transition metal-free approach was developed for the direct difunctionalization of disubstituted alkynes and terminal alkenes with concomitant formation of C-SCF2PO(OEt)2 and C-Cl bonds. The BiCl3-mediated reaction offered access to high value-added functionalized scaffolds in a single operation under mild conditions. Extension to SCF2PO(OEt)2-containing alkynes was also studied.
RESUMO
In recent years, much interest has been paid to difluoromethylthiolated molecules as the "SCF2 " moiety is a key motif in drug and agrochemical research. Consequently, the development of versatile strategies for the selective synthesis of SCF2 H- and SCF2 FG-containing molecules (FG=functional group) has attracted a lot of attention and inspired the scientific community to design new tools. This Minireview highlights the major progress made in this field. Particularly, methodologies developed for the difluoromethylation of sulfur-containing molecules and the direct construction of C-SCF2 bonds in various classes of compounds are showcased and discussed.
RESUMO
An unprecedented electrophilic difluoromethylthiolating reagent (MesNHSCF2 PO(OEt)2 ) was designed. Under mild and metal-free conditions, this new reagent reacted with various nucleophiles, thus offering an efficient and operationally simple tool for the construction of C-SCF2 PO(OR)2 , N-SCF2 PO(OR)2 , and S-SCF2 PO(OR)2 bonds. Finally, thanks to this new methodology, the synthesis of the non-stereoidal anti-inflammatory diflumidone was achieved.
RESUMO
The synthesis of trifluoromethylthiolated aliphatic acid derivatives by Pd-catalyzed C(sp(3))-H bond functionalization was developed. Using a bidentate directing group, the direct and selective introduction of a SCF3 moiety was possible on a range of amides with remarkable selectivity for C(sp(3))-centers with an electrophilic SCF3 source and pivalic acid as an additive. This work constitutes an example of the unactivated C(sp(3))-SCF3 bond formation by C-H activation offering a new access to relevant molecules.
RESUMO
A novel copper-catalyzed one-pot cross-coupling of ß-ketoacids with in situ generated trifluorodiazoethane has been developed. This reaction provides a direct and efficient method, in which one C-C bond and one C-O bond were formed in a carbenoid center with concomitant denitrogenation-dehydrogenation-decarboxylation, to afford trifluoromethylated aldol products. In several preliminary experiments, good to high enantioselectivities were also obtained.
Assuntos
Aldeídos/química , Cobre/química , Cetoácidos/química , Aldeídos/síntese química , Compostos Azo/química , Catálise , Cristalografia por Raios X , Descarboxilação , Hidrocarbonetos Fluorados/química , Metilação , Conformação Molecular , EstereoisomerismoRESUMO
A facile one-pot sequential conjugate addition/dearomative fluorination transformation of isoxazol-5(4H)-ones with nitroolefins and N-fluorobenzenesulfonimide (NFSI) has been developed. By using a bifunctional chiral tertiary amino-thiourea catalyst, a series of chiral fluorinated isoxazol-5(4H)-ones containing one fluorine-substituted quarternary stereocenter were obtained in high yields with high enantio- and diastereoselectivities. Further transformation of adducts could afford isoxazolidin-5-one derivatives with three contiguous stereocenters.
Assuntos
Isoxazóis/química , Sulfonamidas/química , Sulfonamidas/síntese química , Tioureia/química , Catálise , Halogenação , Estrutura Molecular , EstereoisomerismoRESUMO
We disclose an organocatalyzed enantioselective decarboxylative ketone aldol reaction of ß-ketoacids with trifluoromethyl ketones in the presence of biscinchona alkaloid (DHQD)(2)AQN, affording chiral tertiary alcohols in up to 98% yield and 90% ee.
Assuntos
Biomimética/métodos , Cetoácidos/química , Cetonas/química , Catálise , EstereoisomerismoRESUMO
We developed a facile, one-pot, multistep transformation between glycine imine and exocyclic α,ß-unsaturated ketones in reactions catalyzed by chiral phase-transfer catalysts (PTC). A series of polycyclic imines containing three adjacent stereocenters were obtained in good to high yields with high diastereo- and enantioselectivities. Further transformation of the imines could afford N-fused polycyclic compounds with four adjacent stereocenters.