Threefold Coupling Research Articles

Hybridized Exciton-Photon-Phonon States in a Transition Metal Dichalcogenide van der Waals Heterostructure Microcavity

Excitons in atomically thin transition-metal dichalcogenides (TMDs) have been established as an attractive platform to explore polaritonic physics, owing to their enormous binding energies and giant oscillator strength. Basic spectral features of exciton polaritons in TMD microcavities, thus far, were conventionally explained via two-coupled-oscillator models. This ignores, however, the impact of phonons on the polariton energy structure. Here we establish and quantify the threefold coupling between excitons, cavity photons, and phonons. For this purpose, we employ energy-momentum-resolved photoluminescence and spatially resolved coherent two-dimensional spectroscopy to investigate the spectral properties of a high-quality-factor microcavity with an embedded WSe_{2} van der Waals heterostructure at room temperature. Our approach reveals a rich multibranch structure which thus far has not been captured in previous experiments. Simulation of the data reveals hybridized exciton-photon-phonon states, providing new physical insight into the exciton polariton system based on layered TMDs.

Rapid Access to Triarylated Cyclotriveratrylenes from Threefold Couplings of CTV‐I3 with Triarylbismuth Reagents

AbstractA series of C3‐symmetric triiodocyclotriveratrylene (CTV‐I3) derivatives have been successfully arylated to afford the corresponding triarylcyclotriveratrylene derivatives in high yields by using triarylbismuth compounds as threefold coupling reagents under palladium‐catalyzed conditions. This functionalization is valuable in the context of the development of new synthetic and coupling studies to rapidly access cyclotriveratrylene molecular skeletons with rigid and deeper cavities.

ChemInform Abstract: Triarylbismuthanes as Threefold Aryl‐Transfer Reagents in Regioselective Cross‐Coupling Reactions with Bromopyridines and Quinolines.

Cross-coupling studies using bromopyridines and bromoquinolines with triarylbismuths as threefold coupling reagents in substoichiometric amounts under Pd-catalysed conditions are disclosed. The reactivity was high with both mono- and dibromopyridyl substrates, and mono- and bis-couplings were carried out regioselectively. A library of monoaryl and diaryl pyridines was formed in high yields. A one-pot strategy provided a simple and straightforward synthesis of both symmetrical and unsymmetrical diarylpyridines. Arylations of 2-bromo- and 3-bromoquinolines were achieved with triarylbismuth reagents. This study demonstrates that triarylbismuths may be used as threefold arylating reagents for the synthesis of aryl pyridines and quinolines through couplings with bromopyridines and bromoquinolines under Pd-catalysed conditions.

ChemInform Abstract: Pd‐Catalyzed Chemo‐Selective Mono‐arylations and Bis‐arylations of Functionalized 4‐Chlorocoumarins with Triarylbismuths as Threefold Arylating Reagents.

Abstract Cross-coupling reactions of differently substituted 4-chlorocoumarins were studied under palladium catalysis using triarylbismuths as threefold arylating reagents. The high reactivity of 4-chlorocoumarins was demonstrated delivering mono- and bis-arylation products in a chemo-selective manner. The reaction conditions employed are simple, robust and the threefold coupling reactivity of triarylbismuth reagents was witnessed with good to high yields in 2–4 h conditions. The utility of the methodology was explored in the synthesis of a few natural occurring neoflavones ( 3.27 – 3.30 ). In addition, the 4-arylcoumarin 3.1 product is a useful precursor for the preparation of ( R )-tolterodine.

ChemInform Abstract: Threefold and Chemoselective Couplings of Triarylbismuths with Benzylic Chlorides and Iodides Using Palladium Catalysis.

This paper describes the palladium-catalyzed studies on threefold coupling of triarylbismuth reagents with benzylic chlorides and iodides. The optimized protocol conditions are operationally simple, delivering threefold coupling of a variety of triarylbismuths in combination with benzylic chlorides and iodides. The two optimized protocols allowed the synthesis of a diverse range of unsymmetrical diarylmethanes in an efficient manner. As part of this study, chemoselective transformation of benzylic chlorides and iodides was also achieved.

Pd-catalyzed chemo-selective mono-arylations and bis-arylations of functionalized 4-chlorocoumarins with triarylbismuths as threefold arylating reagents

Cross-coupling reactions of differently substituted 4-chlorocoumarins were studied under palladium catalysis using triarylbismuths as threefold arylating reagents. The high reactivity of 4-chlorocoumarins was demonstrated delivering mono- and bis-arylation products in a chemo-selective manner. The reaction conditions employed are simple, robust and the threefold coupling reactivity of triarylbismuth reagents was witnessed with good to high yields in 2–4 h conditions. The utility of the methodology was explored in the synthesis of a few natural occurring neoflavones (3.27–3.30). In addition, the 4-arylcoumarin 3.1 product is a useful precursor for the preparation of (R)-tolterodine.

Triarylbismuthanes as Threefold Aryl‐Transfer Reagents in Regioselective Cross‐Coupling Reactions with Bromopyridines and Quinolines

AbstractCross‐coupling studies using bromopyridines and bromoquinolines with triarylbismuths as threefold coupling reagents in substoichiometric amounts under Pd‐catalysed conditions are disclosed. The reactivity was high with both mono‐ and dibromopyridyl substrates, and mono‐ and bis‐couplings were carried out regioselectively. A library of monoaryl and diaryl pyridines was formed in high yields. A one‐pot strategy provided a simple and straightforward synthesis of both symmetrical and unsymmetrical diarylpyridines. Arylations of 2‐bromo‐ and 3‐bromoquinolines were achieved with triarylbismuth reagents. This study demonstrates that triarylbismuths may be used as threefold arylating reagents for the synthesis of aryl pyridines and quinolines through couplings with bromopyridines and bromoquinolines under Pd‐catalysed conditions.

Preferential oxidative addition in mixed iodo/bromo quinquephenylenes

A Suzuki reaction of a diiodo monobromo quinquephenylene with an aryl boronic acid is described. With PEPPSI-IPr as catalyst the threefold coupling product is mainly obtained although only two equivalents of the boronic acid are used. This shows that the intramolecular palladium transfer is favored over the common iodo/bromo selectivity. Performing the reaction with other Pd systems shows that the product distribution is strongly catalyst dependent.

Threefold and chemoselective couplings of triarylbismuths with benzylic chlorides and iodides using palladium catalysis

This paper describes the palladium-catalyzed studies on threefold coupling of triarylbismuth reagents with benzylic chlorides and iodides. The optimized protocol conditions are operationally simple, delivering threefold coupling of a variety of triarylbismuths in combination with benzylic chlorides and iodides. The two optimized protocols allowed the synthesis of a diverse range of unsymmetrical diarylmethanes in an efficient manner. As part of this study, chemoselective transformation of benzylic chlorides and iodides was also achieved.

The firm/territory relationships in the globalisation: towards a new rationale

– The aim of this paper is the presentation of an approach of firms-territories relationships in terms of firms' nomadism and territorial anchorage of technological and industrial activities. Such an approach is founded on the necessity to overcome the “volatile” firm's level of analysis, in which firm's mobility is investigated from the sole point of view of the leaven location. On the contrary, it should be relevant to focus on the firm's dynamics through its connections with the whole set of territories and to conceive the firm-territory relation as a result of the dialectic confrontation of the respectively concerned firm and territory both dynamics, both trajectories. Hence we are led to characterise the localised industrial unit as placed at the crossroad of a triple link: with a firm (or a group), with an industry and with a territory. Such a threefold coupling relies on proximity's effects, alternately from organisational and geographical nature, whose conjunction generates territorial anchoring and leads to the notion of productive encounter, in the sense of a capacity to formulate and give solutions to productive issues, within the context of firm-territory relationship. In terms of formal models, research works are at the very first step. Nevertheless, an approach in terms of “small worlds” seems to present very fruitful perspectives. We develop the foundations of such an approach and expose how it can provide a good framework to explain territorial anchorage and, more widely, the strength of clusters. A concrete illustration is extensively developed about SGS-Thomson Microelectronics group with regard to its productive site in Rousset, in the French Bouches-du-Rhone district. Classification Codes: L23, L63, O18, R3, R58.

Synthesis of fluorenylidene‐ and 9‐alkylidene‐3,6‐dimethyl‐4,5‐diazafluorene compounds from 2,2′‐biarene‐3,3′‐diyl bis(triflate) by a palladium‐catalyzed domino process

AbstractA convenient synthesis of the fluorenylidene and the 4,5‐diazafluorenylidene moiety is described. The palladium‐catalyzed coupling of 6,6′‐dimethyl‐2,2′‐bipyrdine‐3,3′‐diyl bis(triflate) (2) with phenylacetylene leads to the 4,5‐diazafluorenylidene compound 4 as the major reaction product by an intramolecular cyclization. Under the same conditions biphenyl‐2,2′‐diyl bis(triflate) (6) gives the threefold coupling product 7. The connectivity of 4 and 7 is confirmed by crystal structure analysis.

Acoustic remote sensing instrumentation for sediment transport research

Sediment transport in the oceanic bottom boundary layer involves threefold coupling among: (1) the motion of sediment grains; (2) the response of the bed; and (3) the fluid forcing. The appeal of acoustic remote sensing methods is that in principle all three components of the problem can be addressed with minimal disturbance to the system. This paper reviews the progress that has been made to date toward developing acoustic instrumentation systems for sediment transport measurements in the nearshore zone, where sand is the principal component of the bottom sediments. Instrument developments are discussed in relation to several types of measurement requiring multiple acoustic beams: (1) range-gated multifrequency backscatter to obtain profiles of suspended sediment concentration and size, and the associated inverse problem; (2) bedform imaging with fan-beam sonars; (3) suspended sediment fluctuations under waves. The results provide revealing insights into the sediment transport process, and thus demonstrate the effectiveness of the multibeam approach. The results also raise a number of fundamental questions. Some of these questions can be addressed with the instrumentation currently at hand. Others will require a new generation of instruments.

Theory of nematic order with aggregate dehydration for reversibly assembling proteins in concentrated solutions: Application to sickle-cell hemoglobin polymers.

The reversible association of globular protein molecules in concentrated solution leads to highly polydisperse fibers, e.g., actin filaments, microtubules, and sickle-cell hemoglobin fibers. At high concentrations, excluded-volume interactions between the fibers lead to spontaneous alignment analogous to that in simple lyotropic liquid crystals. However, the phase behavior of reversibly associating proteins is complicated by the threefold coupling between the growth, alignment, and hydration of the fibers. In protein systems aggregates contain substantial solvent, which may cause them to swell or shrink, depending on osmotic stress. Extending previous work, we present a model for the equilibrium phase behavior of the above-noted protein systems in terms of simple intra- and interaggregate interactions, combined with equilibration of fiber-incorporated solvent with the bulk solvent. Specifically, we compare our model results to recent osmotic pressure data for sickle-cell hemoglobin and find excellent agreement. This comparison shows that particle interactions sufficient to cause alignment are also sufficient to squeeze significant amounts of solvent out of protein fibers. In addition, the model is in accord with findings from independent sedimentation and birefringence studies on sickle-cell hemoglobin.