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Research demonstrates a new palladium-catalyzed homocoupling pathway, which is initiated with ethyl bromoacetate. Data indicate that the palladium enolate intermediate undergoes double transmetalation with an alkynyl copper to form diynes in high yields.

Asymmetric hydrogenation of aromatic ketones was examined via s Ru-BICP catalytic system. The results suggested that a Ru-BICP-chiral-diamine KOH catalyst system is affective for hydrogenation of aromatic ketones, especially 2-acetyltiophene derivatives. Moreover, it was also suggested that multipoint interactions between the substrate and the catalysts might be responsible for high enantioselectinity in reduction of 2-acetylthiophene derivatives.

For over half a century, transition‐metal‐catalyzed homogeneous hydrogenation has been mainly focused on neutral and readily prepared unsaturated substrates. Although the addition of molecular hydrogen to C=C, C=N, and C=O bonds represents a well‐studied paradigm, the asymmetric hydrogenation of cationic species remains an underdeveloped area. In this study, we were seeking a breakthrough in asymmetric hydrogenation, with cationic intermediates as targets, and thereby anticipating applying this powerful tool to the construction of challenging chiral molecules. Under acidic conditions, both N‐ or O‐acetylsalicylamides underwent cyclization to generate cationic intermediates, which were subsequently reduced by an iridium or rhodium hydride complex. The resulting N,O‐acetals were synthesized with remarkably high enantioselectivity. This catalytic strategy exhibited high efficiency (turnover number of up to 4400) and high chemoselectivity. Mechanistic studies supported the hypothesis that a cationic intermediate was formed in situ and hydrogenated afterwards. A catalytic cycle has been proposed with hydride transfer from the iridium complex to the cationic sp2 carbon atom being the rate‐determining step. A steric map of the catalyst has been created to illustrate the chiral environment, and a quantitative structure–selectivity relationship analysis showed how enantiomeric induction was achieved in this chemical transformation. [ABSTRACT FROM AUTHOR]

Asymmetric hydrogenation of α,β-unsaturated acids catalyzed by noble metals has been well established, whereas, the asymmetric hydrogenation with earth-abundant-metal was rarely reported. Here, we describe a cobalt-catalyzed asymmetric hydrogenation of α,β-unsaturated carboxylic acids. By using chiral cobalt catalyst bearing electron-donating diphosphine ligand, high activity (up to 1860 TON) and excellent enantioselectivity (up to >99% ee) are observed. Furthermore, the cobalt-catalyzed asymmetric hydrogenation is successfully applied to a broad spectrum of α,β-unsaturated carboxylic acids, such as various α-aryl and α-alkyl cinnamic acid derivatives, α-oxy-functionalized α,β-unsaturated acids, α-substituted acrylic acids and heterocyclic α,β-unsaturated acids (30 examples). The synthetic utility of the protocol is highlighted by the synthesis of key intermediates for chiral drugs (6 cases). Preliminary mechanistic studies reveal that the carboxy group may be involved in the control of the reactivity and enantioselectivity through an interaction with the metal centre. A large number of marketed drugs contains a chiral carboxylic acid scaffold. Here, the authors report the asymmetric hydrogenation of α,β-unsaturated carboxylic acids to α-chiral carboxylic acids using a cobalt catalyst bearing an electron-donating chiral diphosphine ligand. [ABSTRACT FROM AUTHOR]

A Ru‐catalyzed direct asymmetric reductive amination of ortho‐OH‐substituted diaryl and sterically hindered ketones with ammonium salts is reported. This method represents a straightforward route toward the synthesis of synthetically useful chiral primary diarylmethylamines and sterically hindered benzylamines (up to 97 % yield, 93–>99 % ee). Elaborations of the chiral amine products into bioactive compounds and a chiral ligand were demonstrated through manipulation of the removable and convertible ‐OH group. [ABSTRACT FROM AUTHOR]

A Ru‐catalyzed direct asymmetric reductive amination of ortho‐OH‐substituted diaryl and sterically hindered ketones with ammonium salts is reported. This method represents a straightforward route toward the synthesis of synthetically useful chiral primary diarylmethylamines and sterically hindered benzylamines (up to 97 % yield, 93–>99 % ee). Elaborations of the chiral amine products into bioactive compounds and a chiral ligand were demonstrated through manipulation of the removable and convertible ‐OH group. [ABSTRACT FROM AUTHOR]

The iridium‐catalyzed cycloisomerization of various alkynoic acids was successfully developed, and a series of five‐, six‐, and especially seven‐membered unsaturated lactones were constructed with moderate yields and excellent regioselectivities (up to 68% yield, >99:1 rr). In addition, the indole compound can be easily prepared with 75% yield through this efficient synthetic methodology. Moreover, a plausible mechanism for this Ir‐catalyzed cycloisomerization of alkynoic acids was proposed. [ABSTRACT FROM AUTHOR]

The novel synthesis of a family of chiral phosphines with a unique fused bicyclic {2.2.1} ring structure was developed. Pd-catalyzed allylic alkylations with single phosphine complex yielded good enantioselectivities. It was shown that modifying the size of the substituents on the chiral monophosphine affected the selectivity. Furthermore, mechanistic aspects of this reactions were investigated.

A cytochrome c oxidase model that consists of a cobalt(II) porphyrin with a copper(I) triazacyclononane macrocycle fastened on the distal face and an imidazole covalently attached to the proximal face has been synthesized and characterized. Redox titrations with molecular oxygen ([O.sub.2]) and cobaltocene were carried out, and [O.sub.2] was found to bind irreversibly in a 1:1 ratio to the model compound. This [O.sub.2] adduct (a bridged peroxide) can be fully reduced to the deoxygenated form with four equivalents of cobaltocene. The model compound was adsorbed on an edge-plane graphite electrode, and rotating ring-disk voltammetry was used to monitor the electrocatalytic reduction of [O.sub.2]. Four-electron reduction of [O.sub.2] was observed at physiological pH., Oxidative phosphorylation, a process required by all respiring organisms, involves four-electron ([4e.sup.-]) reduction of [O.sub.2] to [H.sub.2]O by the cytochrome c oxidase enzyme family (1-4). The active site of cytochrome [...]