Alkenylation and Allylation of Aldehydes by Using an Ni/Cr/TDAE Redox System

In 360 females, Bone mineral density (BMD) in lumbar vertebrae (L2-L4) was assessed by quantitative computed tomography (QCT), and the values obtained were compared with the frequency of vertebral transformation or fracture as assessed by lateral scan image (scanogram) by X-ray CT. A correlation was observed between the frequency of vertebral transformation (or fracture) and lumbar BMD values : BMD under 125 mg/cm(3) was observed over 90% of women with vertebral transformation, and BMD under 70mg/cm(3) was found about 50% of them. These results suggest that decrease in BMD in lumbar vertebrae leads to vertebral transformation or fracture. Thus, measurement of BMD by QCT would be very useful in predicting vertebral transformation or fractures

Rhenium-Catalyzed Regioselective ortho-Alkenylation and [3 + 2 + 1] Cycloaddition of Phenols with Internal Alkynes

An operationally simple and direct rhenium-catalyzed ortho-alkenylation (C-alkenylation) of unprotected phenols with alkynes was developed. The protocol provided ortho-alkenylphenols exclusively, and formation of para- or multiply alkenylated phenols and hydrophenoxylation (O-alkenylation) products were not observed. The [3 + 2 + 1] cycloaddition of phenols and two alkynes via ortho-alkenylation was also demonstrated, in which the alkynes functioned as both two- and one-carbon units. These reactions proceeded with readily available starting materials under neutral conditions without additional ligands

Substrate-Selective C-H Functionalization for the Preparation of Organosulfur Compounds from Crude Oil-Derived Components

The direct utilization of a natural feedstock in organic synthesis is an utmost challenge because the selective production of one product from a mixture of starting materials requires unprecedented substrate selectivity. In the present study, a simple and convenient procedure is evaluated for the substrate-selective alkenylation of a single component in a mixture of organosulfur compounds. Pd-catalyzed alkenylation of two-, three-, four-, and five-component mixtures of crude oil-derived sulfur species led to the exclusive C–H functionalization of only one compound. The observed remarkable substrate selectivity opens new opportunities for sustainable organic synthesis

Mechanistic Insights into Rhenium-Catalyzed Regioselective C-Alkenylation of Phenols with Internal Alkynes

A (μ-aryloxo)rhenium complex was isolated and confirmed as a key precatalyst for rhenium-catalyzed ortho-alkenylation (C-alkenylation) of unprotected phenols with alkynes. The reaction exclusively provided ortho-alkenylphenols; the formation of para or multiply alkenylated phenols and hydrophenoxylation (O-alkenylation) products was not observed. Several mechanistic experiments excluded a classical Friedel-Crafts-type mechanism, leading to the proposed phenolic hydroxyl group assisted electrophilic alkenylation as the most plausible reaction mechanism. For this purpose, the use of rhenium, a metal between the early and late transition metals in the periodic table, was key for the activation of both the soft carbon-carbon triple bond of the alkyne and the hard oxygen atom of the phenol, at the same time. ortho-Selective alkenylation with allenes also provided the corresponding adducts with a substitution pattern different from that obtained by the addition reaction with alkynes

Palladium-Catalyzed Oxidative Arene C-H Alkenylation Reactions Involving Olefins

The Palladium-catalyzed selective C-H alkenylation reaction has been established as a central synthetic transformation to enable the construction of carbon–carbon bonds in an efficient, atom-economical, and environmentally friendly way. It provides a powerful alternative to classical cross-coupling reactions for the construction of conjugated organic molecules, including late-stage functionalization. The knowledge of mechanisms, the use of different strategies to control site-selectivity, and the development of efficient chiral catalysts for C-H alkenylation reactions has expanded the application of this tool for the synthesis of molecules of increased complexityMinisterio de Ciencia e Innovación (PID2019-104148GB-I00) / / Gobierno Vasco (IT1045-16

C2-Alkenylation of N-heteroaromatic compounds:Via Brønsted acid catalysis

C2-alkenylated heteroaromatics can be accessed by simple Brønsted acid catalysed union of diverse heteroarene N-oxides with alkenes. The scope and limitations of the process are outlined.</p

Ruthenium-Catalyzed Heck-Type Alkenylation of Alkyl Bromides

The complex [Cp*RuCl(PPh3)2] displays a high catalytic activity for the Heck-type alkenylation of alkyl bromides, in the first example using this metal under thermal conditions. The coupling reaction proceeds efficiently with a variety of functionalized tertiary, secondary, and primary alkyl bromides. The presence of Hünig’s base has been revealed crucial for this transformation. Preliminary mechanistic studies support the participation of alkyl radicals in the reaction.We thank MINECO for a grant (CTQ2017-82893-C2-1-R). We also thank Francisco Molina for X-ray structure determinatio

Indole diterpenoid natural products as the inspiration for new synthetic methods and strategies.

Indole terpenoids comprise a large class of natural products with diverse structural topologies and a broad range of biological activities. Accordingly, indole terpenoids have and continue to serve as attractive targets for chemical synthesis. Many synthetic efforts over the past few years have focused on a subclass of this family, the indole diterpenoids. This minireview showcases the role indole diterpenoids have played in inspiring the recent development of clever synthetic strategies, and new chemical reactions

Palladium-Catalysed Functionalisation of Csp3–H Bonds Directed by Aliphatic Amines

Synthetic transformations on medicinally-relevant aliphatic amines are valuable in the diversification of molecules designed as pharmaceutical agents. This thesis describes two Csp3–H functionalisation reactions, using native amines (secondary and tertiary) to direct C–H activation. Chapter 2 describes a palladium-catalysed Csp3–H acetoxylation directed by native secondary amines. A range of cyclic amines could be acetoxylated with excellent functional group tolerance to form the desired functionalised products. Kinetic experiments and DFT calculations elucidated the mechanism of the transformation, which features C–O bond formation via an external acetate attack onto the electrophilic C–Pd bond. Chapter 3 describes a palladium-catalysed Csp3–H alkenylation directed by tertiary aliphatic amines. A diverse set of amines were functionalised using alkenyl boronic ester coupling partners to give the desired olefinated products. The work includes enantioselective functionalisation using a chiral ligand and a preliminary study of stoichiometric aminoalkyl palladium(II) complexes.AstraZenec

Copper-Catalyzed Oxy-Alkenylation of Homoallylic Alcohols to Generate Functional syn-1,3-Diol Derivatives.

A novel method for the synthesis of a wide range of functionalized 1,3-diol derivatives is reported. Employing a copper-catalyzed oxy-alkenylation strategy, a range of readily available, substituted homoallylic alcohol derivatives and alkenyl(aryl) iodonium salts combine to form syn-1,3-carbonates in excellent yield and with high selectivity. Furthermore, the products formed are amenable to an iterative reaction sequence, thus affording highly complex polyketide-like fragments.We are grateful to the EPSRC (D.H.) for a studentship and the ERC and EPSRC for fellowships (M.J.G.).This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1002/anie.20150199