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A simple, regioselective synthesis of di-indole sulfides by electrophilic aromatic substitution of the C3-position of indoles was achieved using Xtalfluor-E as the sulfenylating reagent. The addition of amine bases was found to have a significant effect on the reaction outcome, with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) switching off the reactivity of XtalFluor-E, while the hindered base 2,6-ditertbutyl-4-methylpyridine (DBP) led to the formation of two di-indole-sulfur containing products, one S(II) and one S(IV). The optimal base for accessing the di-indole sulfides in high yield proved to be Hünigs base, EtNi Pr2 . While this amine formed a Lewis adduct with XtalFluor-E, adduct formation did not completely quench electrophilic reactivity indicating reversible coordination to the sulfur centre. This is the first report utilising XtalFluor-E in electrophilic aromatic substitution to form C-S bonds to our knowledge, and this process is applicable to a wide range of functionalised indoles and does not require N1-protection.

The Suzuki–Miyaura (SM) reaction is one of the most important methods for C−C bond formation in chemical synthesis. In this communication, we show for the first time that the low toxicity, inexpensive element zinc is able to catalyze SM reactions. The cross‐coupling of benzyl bromides with aryl borates is catalyzed by ZnBr2, in a process that is free from added ligand, and is compatible with a range of functionalized benzyl bromides and arylboronic acid pinacol esters. Initial mechanistic investigations indicate that the selective in situ formation of triaryl zincates is crucial to promote selective cross‐coupling reactivity, which is facilitated by employing an arylborate of optimal nucleophilicity.

The synergistic interaction of a carbon-centred Lewis acid and borane “hydride shuttle” offers a metal-free, CO tolerant pathway to hydrogen oxidation., Whilst hydrogen is a potentially clean fuel for energy storage and utilisation technologies, its conversion to electricity comes at a high energetic cost. This demands the use of rare and expensive precious metal electrocatalysts. Electrochemical-frustrated Lewis pairs offer a metal-free, CO tolerant pathway to the electrocatalysis of hydrogen oxidation. They function by combining the hydrogen-activating ability of frustrated Lewis pairs (FLPs) with electrochemical oxidation of the resultant hydride. Here we present an electrochemical–FLP approach that utilises two different Lewis acids – a carbon-based N-methylacridinium cation that possesses excellent electrochemical attributes, and a borane that exhibits fast hydrogen cleavage kinetics and functions as a “hydride shuttle”. This synergistic interaction provides a system that is electrocatalytic with respect to the carbon-based Lewis acid, decreases the required potential for hydrogen oxidation by 1 V, and can be recycled multiple times.

A novel intramolecular 1,2-boryl anion migration from boron to carbon has been achieved by selective activation of the π-system in [(vinyl)B2Pin2)]- using “soft” BR3 electrophiles (BR3 = BPh3 or 9-Aryl-BBN). The soft character is key to ensure 1,2-migration proceeds instead of oxygen coordination / B-O activation. The BR3 induced-1,2-boryl anion migration represents a triple borylation of a vinyl Grignard reagent using only B2Pin2 and BR3 and forms differentially protected 1,1,2-triborylated alkanes. Notably, by increasing the steric bulk on the beta position of the vinyl Grignard reagent used to activate B2Pin2, 1,2-boryl-anion migration can be suppressed in favor of intermolecular {BPin} transfer to BPh3, which represents a simple way to access unsymmetrical sp2-sp3 diboranes.

BCl3 is an inexpensive electrophile which induces the borylative cyclization of a wide range of substituted alkynes to regioselectively form polycycles containing synthetically versatile C(sp2)—boronate esters. It proceeds rapidly, with good yields and is compatible with a range of functional groups and substitution patterns. Intermolecular 1,2‐carboboration of alkynes is also achieved using BCl3 to generate trisubstituted vinyl boronate esters.

Frustrated Lewis pair (FLP) chemistry enables a rare example of alkyne 1,2‐hydrocarbation with N‐methylacridinium salts as the carbon Lewis acid. This 1,2‐hydrocarbation process does not proceed through a concerted mechanism as in alkyne syn‐hydroboration, or through an intramolecular 1,3‐hydride migration as operates in the only other reported alkyne 1,2‐hydrocarbation reaction. Instead, in this study, alkyne 1,2‐hydrocarbation proceeds by a novel mechanism involving alkyne dehydrocarbation with a carbon Lewis acid based FLP to form the new C−C bond. Subsequently, intermolecular hydride transfer occurs, with the Lewis acid component of the FLP acting as a hydride shuttle that enables alkyne 1,2‐hydrocarbation.

N−Me-Benzothiazolium salts are introduced as a new family of Lewis acids able to activate Si−H σ bonds. These carbon-centred Lewis acids were demonstrated to have comparable Lewis acidity towards hydride as found for the triarylboranes widely used in Si−H σ-bond activation. However, they display low Lewis acidity towards hard Lewis bases such as Et3PO and H2O in contrast to triarylboranes. The N−Me-benzothiazolium salts are effective catalysts for a range of hydrosilylation and dehydrosilylation reactions. Judicious selection of the C2 aryl substituent in these cations enables tuning of the steric and electronic environment around the electrophilic centre to generate more active catalysts. Finally, related benzoxazolium and benzimidazolium salts were found also to be active for Si−H bond activation and as catalysts for the hydrosilylation of imines.

In contrast to the established dogma that B(C6F5)3 is irreversibly poisoned by excess H2O/amine (or imine) bases, B(C6F5)3 is actually a water-tolerant catalyst for the reductive amination of primary and secondary arylamines with aldehydes and ketones in "wet solvents" at raised temperatures and using only 1.2 equiv of Me2PhSiH as reductant. Arylamines/N-arylimines do not result in the irreversible deprotonation of H2O-B(C6F5)3, allowing sufficient B(C6F5)3 to be evolved at raised temperatures to effect catalytic reductions. Stronger Brønsted basic amines such as tBuNH2 (and derived imines) result in irreversible formation of [HO-B(C6F5)3]- from H2O-B(C6F5)3, precluding the formation of B(C6F5)3 at raised temperatures and thus preventing any imine reduction. A substrate scope exploration using 1 mol % nonpurified B(C6F5)3 and "wet solvents" demonstrates that this is an operationally simple and effective methodology for the production of secondary and tertiary arylamines in high yield, with imine reduction proceeding in preference to other possible reactions catalyzed by B(C6F5)3, including the dehydrosilylation of H2O and the reduction of carbonyl moieties (e.g., esters).