We report the use of a simple complex assembled from Ni(II) salt and 2-mecaptoethanol in one step in water as the efficient catalyst in a molecular hydrogen system which can be sensitized by a low-cost xanthene dye, Erythrosin B. An excellent quantum efficiency of 24.5% is attained at 460 nm. This simple system is expected to contribute toward the development of economical and environmentally benign solar hydrogen production systems.
a b s t r a c tKaempferol is a dietary flavonoid that is thought to function as a selective estrogen receptor modulator. In this study, we established that kaempferol also functions as an inverse agonist for estrogenrelated receptors alpha and gamma (ERRa and ERRc). We demonstrated that kaempferol binds to ERRa and ERRc and blocks their interaction with coactivator peroxisome proliferator-activated receptor c coactivator-1a (PGC-1a). Kaempferol also suppressed the expressions of ERR-target genes pyruvate dehydrogenase kinase 2 and 4 (PDK2 and PDK4). This evidence suggests that kaempferol may exert some of its biological effect through both estrogen receptors and estrogen-related receptors.
Structured summary:MINT-6824653: PGC-1 alpha (uniprotkb:Q9UBK2) and ERR gamma (uniprotkb: P62508) bind (MI:0407) by surface plasmon resonance (MI:0107)
In transition-metal catalyzed, asymmetric α-arylation of carbonyl compounds, formation of tertiary centers with high enantioselectivity is a longstanding problem, due to easy enolization of the monoarylation products. Herein, we report such examples using a palladium catalyst supported by a new, (R)-H(8)-BINOL-derived monophosphine. Silyl ketene acetals, together with a weakly basic activator, were used as equivalents of ester anions, and they reacted smoothly with aryl triflates in excellent enantiomeric excess (ee). The usefulness of the reaction was demonstrated in a gram-scale synthesis of (S)-Naproxen in 92% ee.
Transition-metal-catalyzed a-arylation of carbonyl compounds has become a very useful tool to prepare aarylcarboxylic acids and derivatives. [1] Many asymmetric couplings have been developed for arylation of ketones, [2] aldehydes, [3] oxindoles [4] and a-methylacetoacetates, [5] etc. For example, in a nickel-catalyzed method reported by Hartwig, enolates were formed in situ from cyclic ketones and a strong base. They coupled efficiently with aryl triflates to form quaternary centers with high ee values [Eq. (1), Scheme 1]. [2e] These asymmetric processes cannot be used to construct tertiary centers because arylated products contain acidic aprotons and the latter cannot survive the basic conditions. Thus, arylation of enolates to form tertiary centers must use preformed soft enolates with low basicity. [6] Only recently, MacMillan et al. and Gaunt et al. independently reported arylations of enamines derived from aldehydes as well as silyl enolates of imides to selectively form tertiary centers.[Eq.(2)- (3)]. [7] Reactive diaryliodonium reagents must be used and ketone substrates were not reported. In 2011, we realized the first palladium-catalyzed, highly stereoselective arylation of ester enolates for construction of tertiary centers [Eq. (4)]. [8] In an umpolung approach, Fu et al. reported asymmetric coupling between a-haloketone electrophiles and arylmetal reagents. [9] Herein, we report the first palladiumcatalyzed coupling of ketones to produce tertiary centers with excellent ee values [Eq. (5)].At first, we attempted to couple a silyl enolate of 1tetralone using our ester coupling procedure (2 mol % Pd/ ligand L and LiOAc in PhCF 3 ). However, no product was formed in the presence of LiOAc. With CsF, arylation occurred, but the product racemized. To our delight, we finally found that the tin enolate of 1-tetralone can couple very efficiently with 91 % ee when L1 was used. No erosion of the ee value was observed over time. The tin enolate was formed easily by stirring alkenyl acetate with nBu 3 Sn(OMe) at room temperature, and it was used directly without purification. [10] During catalyst discovery, the Pd(OAc) 2 /difluorphos catalyst, which was previously used by Hartwig et al., [2e] gave poor results with 38 % ee. [Ni(cod) 2 ]/difluorphos (cod = cyclo-1,5-octadiene) was catalytically inactive. [2d] Pd/MOP showed low activity and gave moderate ee values (Scheme 2). We then modified MOP by installing the more donating PCy 2 group and O-2-naphthyl side chain. The resulting L1 turned out to be both active and selective. Structural analogues carrying Scheme 1. Examples of asymmetric coupling of enolates. Tf = trifluoromethanesulfonyl, TMS = trimethylsilyl.
A highly effective hydroxylation reaction of aryl halides with water under synergistic organophotoredox and nickel catalysis is reported. The OH group of the resulting phenols originates from water, following deprotonation facilitated by an intramolecular base group on the ligand. Significantly, aryl bromides as well as less reactive aryl chlorides served as effective substrates to afford phenols with a wide range of functional groups. Without the need for a strong inorganic base or an expensive noble-metal catalyst, this process can be applied to the efficient preparation of diverse phenols and enables the hydroxylation of multifunctional pharmaceutically relevant aryl halides.
Reported herein is the atroposelective synthesis of biaryl NH isoquinolones by RhIII‐catalyzed C−H activation of benzamides and intermolecular [4+2] annulation for a broad scope of 2‐substituted 1‐alkynylnaphthalenes, as well as sterically hindered, symmetric diarylacetylenes. The axial chirality is constructed based on dynamic kinetic transformation of the alkyne in redox‐neutral annulation with benzamides, with alkyne insertion being stereodetermining. The reaction accommodates both benzamides and heteroaryl carboxamides and proceeds in excellent regioselectivity (if applicable) and enantioselectivities (average 91.8 % ee). An enantiomerically and diastereomerically pure rhodacyclic complex was prepared and offers insight into enantiomeric control of the coupling system, wherein the steric interactions between the amide directing group and the alkyne substrate dictate both the regio‐ and enantioselectivity.
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