An extremely electron poor Au(III) trication bearing acetonitrile ligands.

The synthesis and structural characterization of an electron poor Au(III) trication bearing 2 imidazole and 2 acetonitrile ligands is described. The new complex is capable of aryl C-H metalation with the formation of a monomesitylene complex and also demonstrated to be highly oxidizing in the rapid room temperature conversion of cyclohexene to benzene.

A decade of lessons in the activation of ArIL2 species.

Hypervalent iodine(iii) compounds of the general structure ArIL2 are widely used as oxidizing agents for a variety of applications across both organic and inorganic chemistry. Considerable work has been done on the activation of these compounds by tuning the ligands at the iodine centre. This perspective summarises the work of our and other groups on rectification of historically misidentified iodine(iii) reagents of this class, and the syntheses of activated species. Recent advances focusing on increasing the oxidative capacity of I(iii) moieties using Lewis and Brønsted acids and Lewis bases as well as the activation of halogens with I(iii) are discussed.

Formation of Strong Boron Lewis Acid Sites on Silica.

Bis(1-methyl-ortho-carboranyl)borane (HBMeoCb2) is a very strong Lewis acid that reacts with the isolated silanols present on silica partially dehydroxylated at 700 °C (SiO2-700) to form the well-defined Lewis site MeoCb2B(OSi≡) (1) and H2. 11B{1H} magic-angle spinning (MAS) nuclear magnetic resonance (NMR) data of 1 are consistent with that of a three-coordinate boron site. Contacting 1 with O═PEt3 (triethylphosphine oxide TEPO) and measuring 31P{1H} MAS NMR spectra show that 1 preserves the strong Lewis acidity of HBMeoCb2. Hydride ion affinity and fluoride ion affinity calculations using small molecules analogs of 1 also support the strong Lewis acidity of the boron sites in this material. Reactions of 1 with Cp2Hf(13CH3)2 show that the Lewis sites are capable of abstracting methide groups from Hf to form [Cp2Hf-13CH3][H313C-B(MeoCb2)OSi≡], but with a low overall efficiency.

Direct C-H electrophilic borylation with (C6F5)2B-NTf2 to generate B-N dibenzo[a,h]pyrenes.

The borylation of aryl substituted pyridines is an effective way of preparing B-N doped conjugated organic frameworks. Trihaloborane Lewis acids are often employed for this protocol, and may require further functionalization to replace the remaining halides on boron. We report a new, fully characterized, electrophilic borylating agent, (C6F5)2B(κ2-NTf2), that smoothly incorporates a -B(C6F5)2 unit into the model substrate 2-phenylpyridine. To demonstrate its utility in preparing more complex B-N doped structures, we use it to prepare seven examples of the 6a,13a-diaza-7,14-dibora-dibenzo[a,h]pyrene framework, with substituents of varying donor properties. The structural, redox, and photophysical properties of this new family of B-N doped polycyclic hydrocarbon compounds were probed experimentally and computationally.

Electrophilic activation of molecular bromine mediated by I(III).

In pursuit of a genuine bromo-λ3-iodane, it has been found that the combination of Br2 and electron deficient λ3-iodanes can result in the delivery of both bromine atoms from Br2 to a range of aryl substrates, some highly deactivated. These brominations occur rapidly in common chlorinated solvents at room temperature and can be achieved with the catalytic activation of commercially available PhI(OAc)2 and PhI(OTFA)2. para-NO2 substituted derivatives are employed to direct bromination towards more deactivated substrates. The mechanism of Br2 activation is discussed with insights being made, however it remains unclear.

C-H, Si-H and C-F abstraction with an extremely electron poor I(III) reagent.

The recently discovered I(III) reagent NO2-C6H4-I(OTf)2 is found to rapidly react with hydride sources, including HSiEt3 and relatively hydridic C-H precursors. These represent the first distinct reactions involving direct hydride abstraction by I(III) under ambient conditions. Direct C-F abstraction is also demonstrated, as well as oxidation of cyclic alkenes to aromatic rings, all representing new reactions for I(III) demonstrating the very high reactivity of NO2-C6H4-I(OTf)2.

ArI(NTf2)2: the boundary of oxidative capacity for ArIL2?

Synthesis and crystallographic characterization of NO2-C6H4-I(NTf2)2 (NTf2 = bistriflimide) is reported. Experimental results find that this compound can perform oxidation reactions that ArI(OTf)2 is unable to and theoretical analysis indicates Ar-I(NTf2)2 is the most oxidizing in the ArIL2 class of compounds known and may also be the most oxidizing compound in the class practically possible.

The Effect of Carborane Substituents on the Lewis Acidity of Boranes.

The Lewis acidity of primary, secondary, and tertiary boranes with phenyl, pentafluorophenyl, and all three isomers of the C-substituted icosahedral carboranes (ortho, meta, and para) was investigated by computing their fluoride, hydride, and ammonia affinities as well as their global electrophilicity indices and LUMO energies. From these calculations, it was determined that the substituent effects on the Lewis acidity of these boranes follow the trend of ortho-carborane > meta-carborane > para-carborane > C6F5 > C6H5.

Bis(1-Methyl-ortho-Carboranyl)Borane.

The Lewis superacid, bis(1-methyl-ortho-carboranyl)borane, is rapidly accessed in two steps. It is a very effective hydroboration reagent capable of B-H addition to alkenes, alkynes, and cyclopropanes. To date, this is the first identified Lewis superacidic secondary borane and most reactive neutral hydroboration reagent.

A big breakthrough for beryllium.

A stable organometallic compound with a Be-Be bond has been synthesized.

Structural verification and new reactivity for Stang's reagent, [PhI(CN)][OTf].

The structure of Stang's reagent [PhI(CN)][OTf] is confirmed by X-ray crystallography and is determined to be best described as an ion-pair in organic solution. It is found to be a strong Lewis acid, but reaction with pyridine ligands gives [Pyr-CN][OTf] salts via oxidation of pyridine giving a new derivative of the CDAP reagent widely used as an activation agent for polysaccharides.

A focus on coordination chemistry at chlorine.

The first crystallographic characterization of chloronium cations stabilized by pyridine ligands (P. Pröhm, W. Berg, S. M. Rupf, C. Müller and S. Riedel, Chem. Sci., 2023, https://doi.org/10.1039/D2SC06757A) is discussed in the context of coordination chemistry at chlorine.

Synthesis, structural characterization, reactivity and catalytic activity of mixed halo/triflate ArI(OTf)(X) species.

Both mixed λ3-iodoarenes and λ3-iodoarenes possessing -OTf ligands are coveted for their enhanced reactivities. Here we describe the synthesis, reactivity, and comprehensive characterisation of two new ArI(OTf)(X) species, a class of compound that were previously only invoked as reactive intermediates where X = Cl, F and their divergent reactivity with aryl substrates. A new catalytic system for electrophilic chlorination of deactivated arenes using Cl2 as the chlorine source and ArI/HOTf as the catalyst is also described.

Cage hydrocarbons as linkers in dimeric drug design: Case studies with trimethoprim and tedizolid.

The looming threat of a "post-antibiotic era" has been caused by a rapid rise in antibacterial resistance and subsequent depletion of effective antibiotic agents in the clinic. An efficient strategy to address this shortfall lies in the reengineering of pre-existing and commercially available antibiotic drugs. This is exemplified by dimerization, a design concept in which two pharmacophores are covalently linked to form a new chemical entity. The cage hydrocarbons cubane (1), bicyclo[2.2.2]octane (BCO) (2), adamantane (3), and bicyclo[1.1.1]pentane (BCP) (4) present themselves as an attractive family of linkers in this regard. In this report, all four hydrocarbon cages were employed as linkers in a series of dimers based on the commercially available antibiotics trimethoprim and tedizolid. A detailed synthetic roadmap for the protection and deprotection of each pharmacophore is outlined. Several members of the trimethoprim series showed activity on par with that of their trimethoprim progenitor, although this was not the case for the tedizolid series. The design strategy outlined herein highlights the utility of the group as a platform for the rapid and modular construction of future novel antibiotics.

On the potential intermediacy of PhIBr2 as a brominating agent.

PhIBr2, first purported to exist over 100 years ago, has been subject of few reports due to its low stability. However, a recent publication proposes a reaction of PIFA (PhI(OC(O)-CF3)2) with TMSBr to form PhIBr2in situ and demonstrated its efficacy in aryl brominations. This report investigates this synthesis by replicating bromination reactions claiming to use in situ PhIBr2 as described. The spectroscopical and computational results indicate formation of PhI and Br2 where Br2 is responsible for bromination and no supporting evidence for invoking PhIBr2 as an intermediate is found.

Synthesis and Structural Verification of an ArI(OTf)2 , NO2 -Ph-I(OTf)2.

PhI(OTf)2 and related ArI(OTf)2 species have been incorrectly invoked as intermediates in oxidation reactions for many years. We recently established that such compounds did not yet exist but remain an attractive target. Here we describe the synthesis, isolation, and structural characterization of NO2 -PhI(OTf)2, which is resistant to decomposition and more reactive than PhI(OTf)(OAc), the species previously misidentified as PhI(OTf)2 .

Tris(ortho-carboranyl)borane: An Isolable, Halogen-Free, Lewis Superacid.

The synthesis of tris(ortho-carboranyl)borane (BoCb3 ), a single site neutral Lewis superacid, in one pot from commercially available materials is achieved. The high fluoride ion affinity (FIA) confirms its classification as a Lewis superacid and the Gutmann-Beckett method as well as adducts with Lewis bases indicate stronger Lewis acidity over the widely used fluorinated aryl boranes. The electron withdrawing effect of ortho-carborane and lack of pi-delocalization of the LUMO rationalize the unusually high Lewis acidity. Catalytic studies indicate that BoCb3 is a superior catalyst for promoting C-F bond functionalization reactions than tris(pentafluorophenyl)borane [B(C6 F5 )3 ].

An International Study Evaluating Elemental Analysis.

Based on statistical analysis of CHN combustion results of 18 international service providers, it is determined that the ±0.4% deviation most commonly required by chemistry journals is not justified.

Kinetic study on the activation of PhICl2 with Lewis bases for aromatic chlorination.

A study on the kinetics of the activation of PhICl2 using catalytic chloride or pyridine in electrophilic chlorination of arenes has been carried out. The results indicate that both catalysts induce the release of Cl2 from PhICl2 and that the Cl2 is the active reagent for chlorination in these reactions.

Accessing Boron-Doped Pentaphene Analogues from 12-Boradibenzofluorene.

Borole-doped polycyclic aromatic hydrocarbons (PAHs) have garnered attention in recent years due to their attractive photophysical properties and potential utility in electronic devices. In this work, a borole-doped PAH, 12-boradibenzofluorene, is synthesized and formal intermolecular nitrene and oxygen atom insertion reactions were employed to access 1,2-azaborine- and 1,2-oxaborine-containing analogues of the carbonaceous PAH pentaphene. Iodosobenzene is established as a versatile reagent for oxygen atom insertion reactions into a variety of borole species to access 1,2-oxaborine systems.