RESUMO
A new method for the synthesis of benzhydryl amines from the reaction of readily available sulfone derivatives with amines is described. The Cu-catalyzed desulfonylative amination not only provides structurally diverse benzhydryl amines in good yields, but is also applicable to iterative and intramolecular aminations. Control experiments suggested that the formation of a Cu-carbene intermediate generated from the sulfone substrate, which represents a new route for desulfonylative transformations.
RESUMO
A study of the coordination chemistry of different amidato ligands [(R)N-C(Ph)O] (R=Ph, 2,6-diisopropylphenyl (Dipp)) at Groupâ 4 metallocenes is presented. The heterometallacyclic complexes [Cp2M(Cl){κ(2)-N,O-(R)N-C(Ph)O}] M=Zr, R=Dipp (1 a), Ph (1 b); M=Hf, R=Ph (2)) were synthesized by reaction of [Cp2MCl2] with the corresponding deprotonated amides. Complex 1 a was also prepared by direct deprotonation of the amide with Schwartz reagent [Cp2Zr(H)Cl]. Salt metathesis reaction of [Cp2Zr(H)Cl] with deprotonated amide [(Dipp)N-C(Ph)O] gave the zirconocene hydrido complex [Cp2M(H){κ(2)-N,O-(Dipp)N-C(Ph)O}] (3). Reaction of 1 a with Mg did not result in the desired Zr(III) complex but in formation of Mg complex [(py)3Mg(Cl) {κ(2)-N,O-(Dipp)N-C(Ph)O}] (4; py=pyridine). The paramagnetic complexes [Cp'2Ti{κ(2)-N,O-(R)N-C(Ph)O}] (Cp'=Cp, R=Ph (7 a); Cp'=Cp, R=Dipp (7 b); Cp'=Cp*, R=Ph (8)) were prepared by the reaction of the known titanocene alkyne complexes [Cp2'Ti(η(2)-Me3SiC2SiMe3)] (Cp'=Cp (5), Cp'=Cp* (6)) with the corresponding amides. Complexes 1 a, 2, 3, 4, 7 a, 7 b, and 8 were characterized by X-ray crystallography. The structure and bonding of complexes 7 a and 8 were also characterized by EPR spectroscopy.
RESUMO
An efficient and selective bis(amidate)bis(amido) titanium precatalyst for the anti-Markovnikov hydroamination of alkynes is reported. Hydroamination of terminal and internal alkynes with primary alkylamines, arylamines, and hydrazines is promoted by 5-10 mol % of Ti catalyst. Various functional groups are tolerated including esters, protected alcohols, and imines. The in situ generated complex shows comparable catalytic activity, demonstrating its synthetic versatility for benchtop application. Applications of this catalyst for the synthesis of amino alcohols and a one-pot procedure for indole synthesis are described. A mechanistic proposal that invokes turnover-limiting protonolysis is presented to rationalize the observed regioselectivities.
Assuntos
Alcinos/química , Iminas/química , Compostos Organometálicos/síntese química , Titânio/química , Aminação , Catálise , Estrutura MolecularRESUMO
Polycyclic aromatic hydrocarbons (PAHs) are fragments of graphene that have attracted considerable attention as a new class of carbon-based materials. The functionalization of edge positions in PAHs is important to enable the modulation of physical and chemical properties essential for various applications. However, straightforward methods that combine functional group tolerance and regioselectivity remain sought after. Here we report a photochemical approach for the direct alkylation of carbon-hydrogen bonds in PAHs that takes place in a regiospecific manner, an outcome that has never been achieved in related thermal reactions. A reaction mechanism involving a single electron transfer process from photo-excited PAHs to sulfones, and a rationale for the origin of regioselectivity are proposed on the basis of spectroscopic analyses and theoretical calculations.
RESUMO
BACKGROUND: Thyroid hormones (TH) regulate the basal metabolic rate through their receptors THRα and THRß. TH activates lipid metabolism via THRß, however, an excess amount of TH can lead to tachycardia, bone loss, and muscle wasting through THRα. In recent years, TH analogs that selectively bind to THRß have gained attention as new agents for treating dyslipidemia and obesity, which continue to pose major challenges to public health worldwide. METHODS: We developed a TH analog, ZTA-261, by modifying the existing THRß-selective agonists GC-1 and GC-24. To determine the THRß-selectivity of ZTA-261, an in vitro radiolabeled TH displacement assay was conducted. ZTA-261 was intraperitoneally injected into a mouse model of high-fat diet-induced obesity, and its effectiveness in reducing body weight and visceral fat, and improving lipid metabolism was assessed. In addition, its toxicity in the liver, heart, and bone was evaluated. RESULTS: ZTA-261 is more selective towards THRß than GC-1. Although ZTA-261 is less effective in reducing body weight and visceral fat than GC-1, it is as effective as GC-1 in reducing the levels of serum and liver lipids. These effects are mediated by the same pathway as that of T3, a natural TH, as evidenced by similar changes in the expression of TH-induced and lipid metabolism-related genes. The bone, cardiac, and hepatotoxicity of ZTA-261 are significantly lower than those of GC-1. CONCLUSIONS: ZTA-261, a highly selective and less toxic THRß agonist, has the potential to be used as a drug for treating diseases related to lipid metabolism.
Nearly 10% of the world's population suffers from obesity or is overweight. These conditions are closely related to disorders of lipid metabolism, posing significant challenges to individuals and healthcare systems. Thyroid hormone (TH) activates metabolism by binding to specific protein partners, called TH receptors (THRs). There are two types of THRs, THRα and THRß. THRß activates lipid metabolism; however, THRα negatively affects the heart, bone, and muscle when TH is in excess. This study developed a drug called ZTA-261 that selectively binds to THRß. Its administration to mice with induced obesity from a high-fat diet resulted in reduced body fat without any apparent toxicity. Therefore, ZTA-261 is a promising candidate to improve lipid metabolism and address the obesity epidemic.
RESUMO
On the tracks of Schwartz's reagent: Two zirconocene hydrido amidate complexes are synthesized by formal oxidative addition of amide NH bonds to reduced zirconocene fragments. Insertion reactions with alkenes show a different behavior than Schwartz's reagent by forming branched insertion products. The insertion product and the hydrido complex are characterized by X-ray analysis.
RESUMO
A new method for the generation of tertiary radicals through single electron reduction of alkylsulfones promoted by Zn and 1,10-phenanthroline has been developed. These radicals could be employed in the Giese reaction, affording structurally diverse quaternary products in good yields. With the high modularity and functional group compatibility of sulfones, the utility of this method was demonstrated by intramolecular and iterative reactions to give complex structures. The radical generation process was investigated by control experiments and theoretical calculations.
RESUMO
The preparation of a novel Au6 cluster bearing a bidentate mixed carbene-thiolate ligand is presented. The length of linker between the central benzimidazole and thiolate has a strong effect on the formation of cluster products, with a C2 chain giving an Au6 cluster, while a C3 chain results in no evidence of cluster formation. Density functional theory analysis predicts a non-metallic cluster with a large HOMO-LUMO (3.2-3.6 eV) and optical gap.
RESUMO
α-Fluoromethylarenes are common substructures in pharmaceuticals and agrochemicals, with the introduction of fluorine often resulting in improved biological activity and stability. Despite recent progress, synthetic routes to α-fluorinated diarylmethanes are still rare. Herein we describe the Pd-catalyzed Suzuki-Miyaura cross-coupling of α-fluorinated benzylic triflones with arylboronic acids affording structurally diverse α-fluorinated diarylmethanes. The ease of synthesis of fluorinated triflones as the key starting materials enables powerful late-stage transformations of known biologically active compounds into fluorinated analogs.
RESUMO
The Pd-catalyzed desulfonative cross-coupling reaction of benzylic sulfone derivatives with 1,3-oxazoles via a deprotonative pathway has been developed. Broad substrate scope for both sulfone and 1,3-oxazole partners is observed, affording a variety of 1,3-oxazole-containing triarylmethanes. Sulfone partners that are primary benzylic, secondary benzylic, and benzhydryl are all effective. Using this method, the straightforward synthesis of multiply arylated structures has been demonstrated.
RESUMO
Unprotected secondary amines are directly alkylated by C-H functionalization adjacent to nitrogen, thereby opening new routes toward the synthesis of α- and ß-alkylated N-heterocycles. α-Alkylated piperidine, piperazine, and azepane products are prepared from heterocycles and alkenes in an atom-economic reaction with excellent regio- and diastereoselectivity. ß-Alkylated N-heterocycles are synthesized via a scalable one-pot alkylation/cyclization procedure generating 3-methylated azetidines, pyrrolidines, and piperidines.