Themed collection Editor’s Choice: Main group reagents and catalysts in organic reactions
Base-promoted domino-borylation-protodeboronation strategy
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.
Polar organometallic strategies for regioselective C–H metallation of N-heterocyclic carbenes
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.
Diboration of 3-substituted propargylic alcohols using a bimetallic catalyst system: access to (Z)-allyl, vinyldiboronates
A Pd/Cu catalyst system facilitates the diboration of unactivated propargylic alcohols with pentafluoroboronic acid and diboron to generate (Z)-allyl, vinyldiboronates.
Transition-metal-carbene-like intermolecular insertion of a borylene into C–H bonds
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.
Black phosphorus as a metal-free, visible-light-active heterogeneous photoredox catalyst for the direct C–H arylation of heteroarenes
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.
Catalyst and additive-free oxidative dual C–H sulfenylation of imidazoheterocycles with elemental sulfur using DMSO as a solvent and an oxidant
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.
Organophotoredox assisted cyanation of bromoarenes via silyl-radical-mediated bromine abstraction
The transition metal-free conversion of aryl bromides into aromatic nitriles using an organophotocatalyst under visible light irradiation.
Photocatalytic decarboxylative alkenylation of α-amino and α-hydroxy acid-derived redox active esters by NaI/PPh3 catalysis
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.
Frustrated Lewis pair-catalyzed double hydroarylation of alkynes with N-substituted pyrroles
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.
Exploration of a KI-catalyzed oxidation system for direct construction of bispyrrolidino[2,3-b]indolines and the total synthesis of (+)-WIN 64821
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).
Organoaluminum cations for carbonyl activation
A Lewis acidic cationic organoaluminum catalyst is demonstrated to perform aldehyde dimerization and ketone hydrosilylation via a carbonyl activation pathway.
Carbon nitride as a heterogeneous visible-light photocatalyst for the Minisci reaction and coupling to H2 production
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.
Elemental sulfur-promoted one-pot synthesis of 2-(2,2,2-trifluoroethyl)benzoxazoles and their derivatives
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.
Visible light-mediated selective α-functionalization of 1,3-dicarbonyl compounds via disulfide induced aerobic oxidation
A visible light-mediated α-functionalization of 1,3-dicarbonyl compounds with switchable selectivity induced by disulfide is disclosed.
1,1-Phosphinoboration of diazomethanes
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.
Switchable regioselection of C–H thiolation of indoles using different TMS counterions
Simply swapping the counteranions of TMS leads to a switchable regioselectivity in C2– and C3–H thiolation of indoles.
Transition-metal-free Intramolecular C–H amination of sulfamate esters and N-alkylsulfamides
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.
Domino N-/C- or N-/N-/C-arylation of imidazoles to yield polyaryl imidazolium salts via atom-economical use of diaryliodonium salts
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.
A self-catalyzed reaction of 1,2-dibenzoyl-o-carborane with hydrosilanes – formation of new hydrofuranes
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.
Thiocyanate radical mediated dehydration of aldoximes with visible light and air
This work describes the first example of dehydration of aldoximes by an in situ generated radical-based hydrogen abstraction reaction.
P(V) dications: carbon-based Lewis acid initiators for hydrodefluorination
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.
Tris(dimethylamino)silylium ion: structure and reactivity of a dimeric silaguanidinium
The formal dimer of an elusive silaguanidinium ion is described. It undergoes spontaneous electrophilic aromatic silylation of electron rich π-systems.
Carbonyl and olefin hydrosilylation mediated by an air-stable phosphorus(III) dication under mild conditions
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.
Hydroboration without a B–H bond: reactions of the borinium cation [(iPr2N)2B]+ with alkyne, nitrile, ketone and diazomethane
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 induced cooperative B–H bond activation and unprecedented aldehyde C–H bond splitting with amidinate ring expansion
Silylene mediated B–H and aldehyde C–H bond splitting were realized under ambient conditions.
Catalyst and additive-free regioselective oxidative C–H thio/selenocyanation of arenes and heteroarenes with elemental sulfur/selenium and TMSCN
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.
Nitrosonium ion catalysis: aerobic, metal-free cross-dehydrogenative carbon–heteroatom bond formation
Catalytic cross-dehydrogenative coupling of heteroarenes with thiophenols and phenothiazines has been developed under mild and environmentally benign reaction conditions.
Oxidative three-component 1,2-alkylarylation of alkenes with alkyl nitriles and N-heteroarenes
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.
Nucleophilic amination of methoxypyridines by a sodium hydride–iodide composite
A new protocol for nucleophilic amination of methoxypyridines and their derivatives was developed using sodium hydride (NaH) in the presence of lithium iodide (LiI).
NaI-mediated divergent synthesis of isatins and isoindigoes: a new protocol enabled by an oxidation relay strategy
A new approach for the synthesis of isatins and isoindigoes by an inexpensive and environmentally friendly NaI-mediated transformation is disclosed.
Oxidative radical divergent Si-incorporation: facile access to Si-containing heterocycles
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.
A strategy for generating aryl radicals from arylborates through organic photoredox catalysis: photo-Meerwein type arylation of electron-deficient alkenes
Generation of a variety of aryl radicals from arylboronic acids through metal-free photoredox catalysis under mild conditions.
Kinetic stabilisation of a molecular strontium hydride complex using an extremely bulky amidinate ligand
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.
Air- and water-stable Lewis acids: synthesis and reactivity of P-trifluoromethyl electrophilic phosphonium cations
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.
Radical-mediated intramolecular β-C(sp3)–H amidation of alkylimidates: facile synthesis of 1,2-amino alcohols
A new radical-mediated intramolecular β-C(sp3)–H amidation reaction of O-alkyl trichloro- or arylimidates is reported.
About this collection
Collated by ChemComm Chair, Douglas Stephan (University of Toronto, Canada), this collection explores exciting research in the area of main group reagents and catalysts in organic reactions published in the journal. The use of main group species either as stoichiometric reagents or as catalysts is an area that has garnered much attention in the last decade. This area continues to offering new tools for organic synthesis, which are either alternatives or complementary to transition metal catalysts. In this collection, we highlight recent works have that have contributed to this important cutting edge area.