Themed collection Editor’s Choice: Main group reagents and catalysts in organic reactions

Abundant multi-borylated compounds, such as alkyl 1,2-bis(boronates), gem-diborylalkanes and 1,1,2-tris(boronates) are constructed via the base-promoted DBP strategies, which can undergo selective protodeboronation, giving many borylated molecules.

This Feature Article focuses on the recent emergence of s-block metal-mediated N-heterocyclic carbene metallations and the new opportunities this methodology offers to access unique anionic NHC fragments.

A Pd/Cu catalyst system facilitates the diboration of unactivated propargylic alcohols with pentafluoroboronic acid and diboron to generate (Z)-allyl, vinyldiboronates.

In analogy to transition-metal carbene chemistry, [(OC)₅MoBN(SiMe₃)₂] acts as a source of a borylene fragment for selective intermolecular insertion into C–H bonds under very mild conditions.

We report for the first time the employment of black phosphorus (BP) as a metal free, visible-light-active and reusable heterogeneous photoredox catalyst for the direct C–H arylation of heteroarenes (furan and thiophene) with aryl diazonium salts.

A practical, catalyst- and additive-free method for the oxidative dual C–H sulfenylation of imidazoheterocycles with nucleophiles and elemental sulfur using DMSO as both the solvent and oxidant was developed.

The transition metal-free conversion of aryl bromides into aromatic nitriles using an organophotocatalyst under visible light irradiation.

Herein, we report the photocatalytic decarboxylative alkenylation reactions of N-(acyloxy)phthalimide derived from α-amino and α-hydroxy acids with 1,1-diarylethene, and with cinnamic acid derivatives through double decarboxylation, using NaI and PPh₃ as redox catalysts.

Metal-free hydroarylation of alkynes with N-substituted pyrroles is shown to be efficiently mediated by B(C₆F₅)₃ to yield variants of dipyrrole methanes. The mechanism is shown to proceed via an FLP addition pathway.

A facile and environmentally benign KI(cat.)/NaBO₃·4H₂O oxidation system has been developed for the tandem oxidative aminocyclization/coupling of tryptamines, affording a series of 3a,3a′-bispyrrolidino[2,3-b]indolines with high efficiency (up to 94% yield).

A Lewis acidic cationic organoaluminum catalyst is demonstrated to perform aldehyde dimerization and ketone hydrosilylation via a carbonyl activation pathway.

Cyanamide functionalised carbon nitride powder is reported as a photocatalyst for direct Minisci-type coupling of heteroarenes with ethers, alcohols, and amides using atmospheric oxygen or a hydrogen evolving co-catalyst as an electron acceptor.

An elemental sulfur promoted one-pot synthesis of 2-(2,2,2-trifluoroethyl)benzoxazole derivatives from the reaction of o-aminophenols, thiols, and anilines with 2-bromo-3,3,3-trifluoropropene is reported.

A visible light-mediated α-functionalization of 1,3-dicarbonyl compounds with switchable selectivity induced by disulfide is disclosed.

The reactions of the phosphinoboranes Ph₂PBMes₂, Ph₂PBpin, and Ph₂PBcat with the diazomethanes Ph₂CN₂, C₁₂H₈CN₂, and EtO₂CCHN₂ are shown to give products of 1,1-phosphinoboration.

Simply swapping the counteranions of TMS leads to a switchable regioselectivity in C2– and C3–H thiolation of indoles.

The transition-metal-free intramolecular C–H amination of sulfamate esters and N-alkylsulfamides using iodine oxidants, tert-butyl hypoiodite (t-BuOI) and N-iodosuccinimide (NIS) is reported.

A Cu-mediated domino di-/triarylation reaction of imidazoles in a single step by using two aryls as well as an anion of a diaryliodonium salt is developed to quickly achieve polyaryl imidazolium salts.

FLP-type Si–H bond activation by carbonyls in 1,2-dibenzoyl-o-carborane leading to new hydrofuranes with an o-carboranyl backbone in a self-catalyzed reaction.

This work describes the first example of dehydration of aldoximes by an in situ generated radical-based hydrogen abstraction reaction.

The oxidized P(V) dications [(terpy)(C₆Cl₄O₂)PPh]²⁺ and [(terpy)(C₁₄H₈O₂)PPh] are Lewis acidic at the para-carbon of the central ring of the terpy ligand.

The formal dimer of an elusive silaguanidinium ion is described. It undergoes spontaneous electrophilic aromatic silylation of electron rich π-systems.

The air-stable Lewis acid [(terpy)PPh][B(C₆F₅)₄]₂1 mediates the hydrosilylation of aldehydes, ketones, and olefins. The mechanism of these hydrosilylations is considered.

The borinium cation [(iPr₂N)₂B]⁺ (1⁺) is shown to react with PhCCH, PhCN, Ph₂CO, and Ph₂CN₂ to effect a net hydroboration, affording borenium products of 1,1 and 1,2 hydroboration.

Silylene mediated B–H and aldehyde C–H bond splitting were realized under ambient conditions.

Elemental sulfur/selenium and TMSCN act as a novel combined thio/selenocyanation source for direct oxidative C–H thio/selenocyanation of (hetero)arenes under catalyst-free and additive-free conditions.

Catalytic cross-dehydrogenative coupling of heteroarenes with thiophenols and phenothiazines has been developed under mild and environmentally benign reaction conditions.

Indium-promoted oxidative three-component 1,2-alkylarylation of alkenes with alkyl nitriles and N-heteroarenes is achieved by C(sp³)–H/C(sp²)–H functionalization.

A new protocol for nucleophilic amination of methoxypyridines and their derivatives was developed using sodium hydride (NaH) in the presence of lithium iodide (LiI).

A new approach for the synthesis of isatins and isoindigoes by an inexpensive and environmentally friendly NaI-mediated transformation is disclosed.

Oxidative radical cleavage of Si–H/silyl C(sp³)–H bonds, dual Si–H bonds and Si–H/Si–Si bonds toward Si-heterocycles is presented.

Generation of a variety of aryl radicals from arylboronic acids through metal-free photoredox catalysis under mild conditions.

The first dimeric strontium hydride complex (see picture, Dip = 2,6-diisopropylphenyl, Ad = 1-adamantyl), and analogous magnesium hydride systems, have been kinetically stabilised by extremely bulky amidinate ligands, developed for this study.

Electrophilic phosphonium cations (EPCs) containing a –CF₃ group are stable to air, water, alcohol and strong Brønsted acid and function as Lewis acid catalysts without requiring anhydrous reaction conditions.

A new radical-mediated intramolecular β-C(sp³)–H amidation reaction of O-alkyl trichloro- or arylimidates is reported.