Correction: Acridine-based copper(I) PNP pincer complexes: catalysts for alkyne hydroboration and borylation of aryl halides.

Correction for 'Acridine-based copper(I) PNP pincer complexes: catalysts for alkyne hydroboration and borylation of aryl halides' by Angus Olding , , 2024, , 4471-4478, https://doi.org/10.1039/D3DT04269C.

Acridine-based copper(I) PNP pincer complexes: catalysts for alkyne hydroboration and borylation of aryl halides.

PNP pincers represent some of the most well-studied ligand systems in coordination chemistry owing to their high thermal and chemical stability, and the predictable metal coordination geometries of associated metal complexes. Examples of first-row transition metal complexes bearing acridine-based PNP pincer ligands are extremely rare. This study reports the preparation and structural authentication of acridine-based copper(I) PNP complexes, which reveal the profound effects that the steric bulk of methylene-tethered -substituents has on metal centre coordination number and geometry.

Exploring the Excited States of a Hexa--hexabenzocoronene-Substituted Dipyridophenazine Ligand and Its Metal Complexes.

A hexa--hexabenzocoronene (HBC)-substituted dipyridophenazine (dppz) ligand (dppz-HBC) and its corresponding rhenium [Re(CO)Cl] and ruthenium [Ru(bpy)] complexes were synthesized and characterized. The interplay of their various excited states was investigated using spectroscopic and computational techniques. Perturbation of the HBC was seen through a broadening and decreased intensity of the HBC absorption bands that dominate the absorption spectra.

Dipole-Transmissive 1,3-Dipolar Cycloadditions for the Rapid Construction of Polycyclic N-Heterocycles: Synthetic and Mechanistic Investigations.

The investigation of distinctive dipole-transmissive dipolar cycloaddition (DTDC) methodology and the formalisation of this concept is reported. A DTDC procedure was able to be developed by taking advantage of the structural complementarity of azide and diazoalkane 1,3-dipoles. Intramolecular azide-alkene 1,3-DCs followed by spontaneous dipole transmission upon work-up furnished intermediate α-diazoisoindole and α-diazoisoquinoline substrates bearing the key secondary diazoalkane 1,3-dipole.

Pretransmetalation Intermediates in Suzuki-Miyaura Cross-Couplings: Synthesis of C-, C- and C-Organopalladium(II) Boronates.

Organopalladium(II) boronates represent fundamental pretransmetalation intermediates in Suzuki-Miyaura cross-couplings. These species are typically kinetically unstable, making them particularly elusive. In this study, a range of unprecedented, kinetically stable alkyl-, alkenyl-, allenyl-, and alkynylpalladium(II) boronates were prepared from various C, C, and C electrophiles via a simple, general method.

Halimane Diterpenes in the Alpine Daisy : Absolute Configuration, 2,6-Dideoxyhexopyran-3-ulosides, Conformational Flexibility, and Intraspecific Variation.

The methyl-migrated bicyclic skeleton of the halimane diterpenes has been found in a wide range of organisms, including flowering plants, liverworts, marine animals, and bacteria. The discovery of halima-1(10),14-dien-13-ol () from the Aotearoa New Zealand endemic alpine daisy is now reported. The full configuration was assigned for the first time by X-ray crystallography, enantiomeric to that of a liverwort isolate.

-Acylated Flavones in the Alpine Daisy : Intraspecific Variation.

Flavonoids acylated on their core phenolic groups are rare. The Aotearoa New Zealand endemic alpine daisy is widespread, but its flavonoids have not previously been identified. Leaf extracts yielded a series of 8--acylated flavones with combinations of 3-methylbutanoate, 2-methylbutanoate, and 2-methylpropanoate groups and one, two, or three -methyls, all previously unreported.

Exploring Cyclization Strategies to Access Alkaloids: Subtle Effects Influencing Reactivity in Intramolecular Michael Additions.

This report investigates the fundamental basis for rather surprising patterns of reactivity in Brønsted acid-mediated cyclizations of pyrrole substrates bearing pendant Michael acceptors that were identified during syntheses of alkaloids. Integrated experimental and theoretical studies reveal the profound influence that substituent effects have on the viability of these transformations. Additionally, we identify that electronic effects, in addition to barrier-lowering secondary orbital interactions within transition states, account for the exclusive preference for 7--trig cyclizations over 6--trig cyclizations.

Rigid, biconical hydrogen-bonded dimers that strongly encapsulate cationic guests in solution and the solid state.

The octol of a new rigid, tetraarylene-bridged cavitand was investigated for self-assembly behaviour in solution. H and DOSY NMR spectroscopic experiments show that the cavitand readily dimerizes through an unusual seam of interdigitated hydrogen-bonds that is resistant to disruption by polar co-solvents. The well-defined cavity encapsulates small cationic guests, but not their neutral counterparts, restricting the conformation of sequestered tetraethylammonium in solution and the solid state.

Revised Structures of Dehydrostenines A and B: Total Syntheses of (±)-Dehydrostenine A and Structure Assigned to Dehydrostenine B.

The first total syntheses of the Stemona alkaloid dehydrostenine A and the structure assigned to dehydrostenine B have been completed from a simple pyrrole substrate in 10 and 11 steps, respectively. Two independent Brønsted-acid-mediated intramolecular Michael additions were exploited to construct the tetracyclic dehydrostenine core. As a result of synthetic studies and associated analysis of the relevant literature, revisions of the structures originally assigned to dehydrostenines A and B are proposed.

Synthesis of Arylpalladium(II) Boronates: Confirming the Structure and Chemical Competence of Pre-transmetalation Intermediates in the Suzuki-Miyaura Reaction.

Palladium(II) boronates are recognized as fundamental pre-transmetalation intermediates in Suzuki-Miyaura cross-couplings. While these typically transient species have been detected and studied spectroscopically, it is conspicuous that they have never been isolated since this important reaction was discovered over forty years ago. This study reports the synthesis of a family of unprecedented arylpalladium(II) boronates that are, by design, kinetically stable at ambient temperature, both in solution and in the solid state.

Photochemical Activation of a Hydroxyquinone-Derived Phenyliodonium Ylide by Visible Light: Synthetic and Mechanistic Investigations.

We have identified and extensively investigated the photochemical activation and reaction of a hydroxyquinone-derived phenyliodonium ylide in the presence of visible light using experiment and theory. These studies revealed that in its photoexcited state this iodonium is capable of facilitating a range of single-electron transfer (SET) processes, including hydrogen atom transfer (HAT), a Povarov-type reaction, and atom-transfer radical addition chemistry. Where possible, we have employed density functional theory (DFT) to develop a more complete understanding of these photoinduced synthetic transformations.

Transitioning from Intraligand π,π* to Charge-Transfer Excited States Using Thiophene-Based Donor-Acceptor Systems.

A series of electron donor-acceptor compounds are reported in which both the donor and acceptor strengths are systematically altered using mono-, bi-, and terthiophene as donors and benzo[][1,2,5]thiadiazole (btd), dipyrido[3,2-:2',3'-]phenazine (dppz), and the corresponding rhenium(I) complex, [ReCl(CO)(dppz)], as acceptors. The electronic properties of the compounds are characterized using electrochemistry, electronic absorbance and emission spectroscopies, and transient absorption spectroscopy. The effect of donor and acceptor strengths on frontier molecular orbital localization and on the charge-transfer (CT) character of optical transitions is modeled using density functional theory (DFT) calculations.

One-Step Synthesis of -Symmetric Resorcin[4]arene Tetraethers.

The three-component reaction between a resorcinol, 1,3-dimethoxybenzene, and an alkyl aldehyde (R = C-C) along with BF·OEt affords a -symmetric resorcin[4]arene tetraether in one step; in most cases, the single isomer can be precipitated from the reaction mixture in moderate to excellent yields (up to 89%). The reaction is tolerant of 2-substituted resorcinols (R' = OH, Cl, Br, Me), allowing a third type of functionality to be regioselectively incorporated during the macrocyclization.

Generation of Microsecond Charge-Separated Excited States in Rhenium(I) Diimine Complexes: Driving Force Is the Dominant Factor in Controlling Lifetime.

A transition-metal-based donor-(linker)-acceptor system can produce long-lived charge transfer excited states using visible excitation wavelengths. The ground- and excited-state photophysical properties of a series of [ReCl(CO)(dppz-(linker)-TPA)] complexes, with varying donor and acceptor energies, have been systematically studied using spectroscopic techniques (both vibrational and electronic) supported by computational chemistry. The long-lived excited state is ILCT in nature for all complexes studied, characterized through transient absorption and emission, transient resonance Raman (TR), and time-resolved infrared (TRIR) spectroscopy and TDDFT calculations.

Benzannulated 6,5-Spiroketals from Donor-Acceptor Cyclopropanes.

A rapid and facile synthesis of benzannulated 6,5-spiroketals from vinyl 1,1-diacylcyclopropanes is reported. The method utilizes mild reaction conditions with good to excellent yields and high diastereoselectivity. This methodology was then used to construct the core of berkelic acid.

Synthesis of Cyclopenta-HBCs and their Regioselective Chlorination During Oxidative Cyclodehydrogenation.

Hexa-peri-hexabenzocoronenes with a bay-fused five-membered ring are synthesized from fluorenyl precursors. The key oxidative cyclodehydrogenation step is accompanied by regioselective chlorination that is enhanced by methylation at the cyclopenta-ring or increased reaction concentration. The CpHBC products undergo mild electrophilic aromatic bromination, without catalyst, to afford adducts suitable for π-extension by cross-coupling.

Walking the Emission Tightrope: Spectral and Computational Analysis of Some Dual-Emitting Benzothiadiazole Donor-Acceptor Dyes.

The synthesis, spectroscopic characterization, and computational modeling of seven benzo[ c][2,1,3]thiadiazole-based donor-acceptor dyes is reported. Using a range of linker units, it is possible to alter the lowest energy transition in terms of intensity (from 8000 to 25000 L mol cm) and wavelength (from 350 to 430 nm). Resonance Raman spectroscopy was used in concert with DFT calculations to indicate that the linker unit participates in charge transfer processes.

Strategies, Setbacks, and Successes in the Synthesis of (-)-Spiroleucettadine.

Various strategies toward the synthesis of the marine natural product (-)-spiroleucettadine are described. In the original strategy, a biomimetic inspired oxidation of a 2-imidazoline scaffold uncovered unexpected reactivity, where benzylic oxidation followed by a Baeyer-Villiger reaction was observed. The second generation approach examined oxidative dearomatization of the phenol ring system first, where a competing spirocyclization process was uncovered.

Rigid tetraarylene-bridged cavitands from reduced-symmetry resorcin[4]arene derivatives.

Container molecules (cavitands) derived from resorcin[4]arene are of broad interest in supramolecular chemistry as hosts and fragments of larger constructs. Herein is presented a new class of rigid cavitand where the resorcin[4]arene carbon framework is extended with four bridging arylene rings. Two tenable, isomeric precursors of differing symmetry (C and C) were prepared, of which only one afforded the desired fused bowl.

Dramatic Alteration of ILCT Lifetimes Using Ancillary Ligands in [Re(L)(CO)(phen-TPA)] Complexes: An Integrated Spectroscopic and Theoretical Study.

The ground and excited state photophysical properties of a series of fac-[Re(L)(CO)(α-diimine)] complexes, where L = Br, Cl, 4-dimethylaminopyridine (dmap) and pyridine (py) have been extensively studied utilizing numerous electronic and vibrational spectroscopic techniques in conjunction with a suite of quantum chemical methods. The α-diimine ligand consists of 1,10-phenanthroline with the highly electron donating triphenylamine (TPA) appended in the 5 position. This gives rise to intraligand charge transfer (ILCT) states lying lower in energy than the conventional metal-to-ligand charge transfer (MLCT) state, the energies of which are red and blue-shifted, respectively, as the ancillary ligand, L becomes more electron withdrawing.

Superphenylphosphines: Nanographene-Based Ligands That Control Coordination Geometry and Drive Supramolecular Assembly.

Tertiary phosphines remain widely utilized in synthesis, most notably as supporting ligands in metal complexes. A series of triarylphosphines bearing one to three hexa-peri-hexabenzocoronene (HBC) substituents has been prepared by an efficient divergent route. These "superphenylphosphines", P{HBC(t-Bu)}Ph (n = 1-3), form the palladium complexes PdClL and PdClL where the isomer distribution in solution is dependent on the number of HBC substituents.

Alteration of Intraligand Donor-Acceptor Interactions Through Torsional Connectivity in Substituted Re-dppz Complexes.

The ground- and excited-state properties of a series of [ReCl(CO)(dppz)] complexes with substituted donor groups were investigated. Alteration of donor-acceptor communication through modulation of torsional angle and the number and nature of the donor substituents allowed the effects on the photophysical properties to be characterized though both computational and spectroscopic techniques, including time-dependent density functional theory and resonance Raman and time-resolved infrared spectroscopy. The ground-state optical properties show significant variation as a result of donor group modulation, with an increased angle between the donor and acceptor blue-shifting and depleting the intensity of the lowest-energy transition, which is consistently intraligand charge transfer (ILCT) in nature.

Total Synthesis of (-)-Spiroleucettadine.

One of a number of intriguing new alkaloids isolated from the Leucetta sp. sponge in 2004, spiroleucettadine displayed unique structural features on a restricted scaffold: a trans-fused 5,5-bicyclic ring system together with an amino hemiketal moiety. Attempts to synthesize the initially proposed structure failed, raising questions as to its veracity, and structure revision ensued in 2008; no successful synthetic approach has been reported to date.

Octahedral [Pd L ] Metallosupramolecular Cages: Synthesis, Structures and Guest-Encapsulation Studies.

Four planar tripyridyl ligands (L ), 1,3,5-tris(pyridin-3-ylethynyl)benzene 1 a, 1,3,5-tris[4-(3-pyridyl)phenyl]benzene 2 a, and the hexyloxy chain functionalized derivatives 1,3,5-tris[(3-hexyloxy-5-pyridyl)ethynyl]benzene 1 b, and 1,3,5-tris[4-(3-hexyloxy-5-pyridyl)phenyl]benzene 2 b, were synthesized and used to generate a family of [Pd (L ) ](BF ) octahedral cages (L =1 a, b or 2 a, b). The ligands and cages were characterized using a combination of H, C, and DOSY nuclear magnetic resonance (NMR) spectroscopy, high resolution electrospray mass spectrometry (HR-ESI-MS), infrared (IR) spectroscopy, elemental analysis, and in three cases, X-ray crystallography. The molecular recognition properties of the cages with neutral and anionic guests were examined, in dimethyl sulfoxide (DMSO), using NMR spectroscopy, mass spectrometry and molecular modeling.