Synthesis of Tertiary Fluorides through an Acid-Mediated Deoxyfluorination of Tertiary Alcohols

The combination of methanesulfonic acid and potassium bifluoride is reported for the deoxyfluorination of tertiary alcohols. Under metal-free conditions that use readily available, cheap, and easy-to-handle reagents, a range of tertiary alcohols could be converted into the corresponding fluorides in excellent yields (average yields of 85% for 23 examples). Mechanistic investigation showed that the reaction proceeds at 0 °C, in part, through an elimination/hydrofluorination pathway, but no residual alkenes are observed. The application of these conditions for the fluorination of ether and ester is also demonstrated.

Recent Advances in the Synthesis of Borinic Acid Derivatives

Borinic acids [R2B(OH)] and their chelate derivatives are a subclass of organoborane compounds used in cross-coupling reactions, catalysis, medicinal chemistry, polymer or optoelectronics materials. In this paper, we review the recent advances in the synthesis of diarylborinic acids and their four-coordinated analogs. The main strategies to build up borinic acids rely either on the addition of organometallic reagents to boranes (B(OR)3, BX3, aminoborane, arylboronic esters) or the reaction of triarylboranes with a ligand (diol, amino alcohol, etc.). After general practical considerations of borinic acids, an overview of the main synthetic methods, their scope and limitations is provided. We also discuss some mechanistic aspects.

In situ generation of radical initiators using amine-borane complexes for carbohalogenation of alkenes

Atom transfer radical addition of alkyl halides to alkenes was developed using a low amount of a stable initiator, amine borane complexes.

Correction: Amine-borane complex-initiated SF5Cl radical addition on alkenes and alkynes

[This corrects the article DOI: 10.3762/bjoc.16.256.].

Using Catalysts To Make Catalysts: Titanium-Catalyzed Hydroamination To Access P,N-Ligands for Assembling Catalysts in One Pot

Using a diamido-bis(amidate) titanium precatalyst, the hydroamination of alkynylphosphines afforded phosphinoenamine products. After reduction, 2-aminophosphines are prepared in excellent yield and on gram scale. A broad variety of alkynylphosphines and primary amines with different electronic and steric features are tolerated in this sequential transformation, enabling the rapid assembly of a collection of ligands. Additionally, intermediate phosphinoenamines can be used directly as proligands for coordination to transition metals using protonolysis or salt metathesis reactions. These transformations result in easy-to-use one pot protocols to prepare metal P,N-complexes for catalysis or small molecule activation.

Synthesis and Characterization of Store-Operated Calcium Entry Inhibitors Active in the Submicromolar Range

The store-operated calcium entry, better known as SOCE, forms the main Ca²⁺ influx pathway in non-excitable cells, especially in leukocytes, where it is required for cell activation and the immune response. During the past decades, several inhibitors were developed, but they lack specificity or efficacy. From the non-specific SOCE inhibitor 2-aminoethyl diphenylborinate (2-APB), we synthetized 16 new analogues by replacing/modifying the phenyl groups. Among them, our compound P11 showed the best inhibitory capacity with a K_i ≈ 75 nM. Furthermore, below 1 µM, P11 was devoid of any inhibitory activity on the two other main cellular targets of 2-APB, the IP₃ receptors, and the SERCA pumps. Interestingly, Jurkat T cells secrete interleukin-2 under phytohemagglutinin stimulation but undergo cell death and stop IL-2 synthesis when stimulated in the presence of increasing P11 concentrations. Thus, P11 could represent the first member of a new and potent family of immunosuppressors.

Amine-borane complex-initiated SF5Cl radical addition on alkenes and alkynes

The SF5Cl radical addition on unsaturated compounds was performed using an air-stable amine-borane complex as the radical initiator. This method showed to be complementary to the classic Et3B-mediated SF5Cl addition on alkenes and alkynes. A total of seven alkene and three alkyne derivatives were tested in the reaction, with yields ranging from 3% to 85%.

Zirconium-Catalyzed Synthesis of Alkenylaminoboranes: From a Reliable Preparation of Alkenylboronates to a Direct Stereodivergent Access to Alkenyl Bromides

A simple procedure has been optimized for the preparation of alkenylaminoborane from alkynes using diisopropylaminoborane and HZrCp₂Cl. Coupled with a magnesium-catalyzed dehydrogenation, it allowed for the use of air- and moisture-stable diisopropylamine. This synthesis has been extended to a one-pot sequence leading directly to bromoalkenes with controlled stereochemistry. As such, it provides an easy, scalable, cheap process to access alkenylboronates and both (E)- and (Z)-bromoalkenes from commercially available alkynes.

Non-biaryl atropisomerism at the C–B bond in sterically hindered aminoarylboranes

Sterically hindered aminoarylboranes with atropisomerism about the C–B bond were prepared and resolved by chiral stationary phase HPLC.

Radical Metal-Free Borylation of Aryl Iodides

A simple metal-free borylation of aryl iodides mediated by a fluoride sp2–sp3 diboron adduct is described. The reaction conditions are compatible with various functional groups. Electronic effects of substituents do not affect the borylation while steric hindrance does. The reaction proceeds via a radical mechanism in which pyridine serves to stabilize the boryl radicals, generated in situ.

Simple salts of abundant metals (Fe, Bi, and Ti) supported on montmorillonite as efficient and recyclable catalysts for regioselective intramolecular and intermolecular hydroalkoxylation reactions of double bonds and tandem processes

Montmorillonites doped with metal cations are efficient and recyclable catalysts for hydroalkoxylation reactions and amenable to flow chemistry.

Synthesis of Borinic Acids and Borinate Adducts Using Diisopropylaminoborane

In situ formation of aryl Grignard under Barbier condition and diisopropylaminoborane as boron source allows a complete control of the addition onto the boron electrophile. Analytically pure borinic acid derivatives were produced at the gram scale without column chromatography and isolated as borinates adducts, with ethanolamine or 8-hydroxyquinoline, after workup.

Borylation of unactivated aryl chlorides under mild conditions by using diisopropylaminoborane as a borylating reagent

The synthesis of arylboronic ester derivatives from aryl chlorides by using aryl(amino)boranes is described. Palladium-catalyzed coupling between aryl chlorides and diisopropylaminoborane leads to the formation of a CB bond under mild conditions. A wide range of functional groups are tolerated, making this method particularly useful for the borylation of functionalized aromatics.

Glycosylation with N-acetyl glycosamine donors using catalytic iron(iii) triflate: from microwave batch chemistry to a scalable continuous-flow process

Efficient glycosylation reactions of peracetylated β-d-N-acetyl glycosamines are described using catalytic iron(iii) triflate under microwave conditions or in a continuous flow process.

Catalysed stereodivergent hydrosilylation with Onium Salts stabilised M(0) nanocatalysts prepared in scCO2

M(0) nanocatalysts stabilised in Onium Salt were synthesised using an original preparation and their effectiveness in catalysing the challenging selective sterodivergent alkyne hydrosilylation reaction was studied.

Continuous coflow synthesis of hybrid palladium nanocrystals as catalysts for borylation reaction

The combination of highly active Pd nanocrystal (NC) types with tailored surface properties (various ligands) - e.g. organic-inorganic hybrid NCs - as catalysts opens avenues towards new synthetic pathways, implying a faster practical alternative for adjusting and screening the reaction conditions. Pd@dppf and Pd@PCy3 NCs have been successfully prepared via a continuous supercritical fluid assisted coflow route with promising results as catalysts in borylation reaction. It has been found that the ligands not only influence the catalytic properties of the systems, but also contribute to Pd metal core characteristics (size, shape and time stability).

Supercritical synthesis of biodiesel

The synthesis of biodiesel fuel from lipids (vegetable oils and animal fats) has gained in importance as a possible source of renewable non-fossil energy in an attempt to reduce our dependence on petroleum-based fuels. The catalytic processes commonly used for the production of biodiesel fuel present a series of limitations and drawbacks, among them the high energy consumption required for complex purification operations and undesirable side reactions. Supercritical fluid (SCF) technologies offer an interesting alternative to conventional processes for preparing biodiesel. This review highlights the advances, advantages, drawbacks and new tendencies involved in the use of supercritical fluids (SCFs) for biodiesel synthesis.

Aminoborylation/Suzuki-Miyaura tandem cross coupling of aryl iodides as efficient and selective synthesis of unsymmetrical biaryls

Sequential borylation of a first aryl iodide using a dialkylaminoborane followed by a Suzuki-Miyaura cross coupling of second aryl iodide ended up with an efficient, selective and practical synthesis of unsymmetrical biaryls. This tandem coupling shows a wide range of applicability.

Protein chemical modification on endogenous amino acids

Chemical modification of protein is an arduous but fruitful task. Many chemical methods have been developed for such purpose by carefully balancing reactivity and selectivity. Now both chemists and biologists have in hand an arsenal of tools from which they can select a relevant reaction to tackle their problems. This review focuses on the various chemical transformations available for selective modification of proteins. It also provides a brief overview of some of their main applications, including detection of protein interactions, preparation of bioconjugates, and protein microarrays.

Targeted intracellular protein degradation induced by a small molecule: En route to chemical proteomics

We have developed a heterobifunctional all-small molecule PROTAC (PROteolysis TArgeting Chimera) capable of inducing proteasomal degradation of the androgen receptor. This cell permeable PROTAC consists of a non-steroidal androgen receptor ligand (SARM) and the MDM2 ligand known as nutlin, connected by a PEG-based linker. The SARM-nutlin PROTAC recruits the androgen receptor to MDM2, which functions as an E3 ubiquitin ligase. This leads to the ubiquitination of the androgen receptor, and its subsequent degradation by the proteasome. Upon treatment of HeLa cells with 10microM PROTAC for 7h, we were able to observe a decrease in androgen receptor levels. This degradation is proteasome dependent, as it is mitigated in cells pre-treated with 10microM epoxomicin, a specific proteasome inhibitor. These results have implications for the potential study and treatment of various cancers with increased androgen receptor levels.

Natural products: chemical instruments to apprehend biological symphony

As a striking variety of biological activities are elicited by natural products, these chemicals have been used for decades to study biological phenomena. Understanding how these products interfere with normal cell functions at a molecular level led to a wide range of discoveries including new signaling pathways and proteins. Moreover, as natural products often act as chemical inhibitors, such studies often allow the identification of their binding partners as relevant targets for drug design. This article aims to emphasize how natural products or engineered analogs can be used as chemical tools to apprehend some biological problems from the point of view of a chemical biologist.

Carbinol derivatives via rhodium-catalyzed addition of potassium trifluoro(organo)borates to aldehydes

Reaction of potassium aryltrifluoroborates with aldehydes, in the presence of a rhodium catalyst, afforded carbinol derivatives in high yields under mild aqueous conditions; this efficient reaction proved to be general, allowing the production of highly hindered diarylmethanols and aliphatic aldehydes were also reactive under these conditions.

Direct Access to Ketones from Aldehydes via Rhodium-Catalyzed Cross-Coupling Reaction with Potassium Trifluoro(organo)borates

A direct cross-coupling reaction of aromatic aldehydes with potassium trifluoro(organo)borates afforded ketones in high yields and under mild conditions in the presence of a rhodium catalyst and acetone. This new reaction, involving a formal aldehyde C-H bond activation, is believed to proceed via a Heck-type mechanism followed by hydride transfer to acetone.