Tetraarylethylenes from Diarylmethanones and Hexachlorodisilane: The “Sila‐McMurry” Reaction

Hexachlorodisilane reacts with diarylmethanones (aryl=C₆H₅, 4‐MeC₆H₄, 4‐tBuC₆H₄, 4‐ClC₆H₄, 4‐BrC₆H₄) to furnish the corresponding tetraarylethylenes in good yields. The reductive conversion requires temperatures of about 160 °C and reaction times of 60–72 h. In the initial step, the Lewis‐basic carbonyl groups likely generate low‐valent [SiCl₂] as an analogue of [TiCl₂] in the classical McMurry reaction. The coupling sequence further proceeds via benzopinacolones, which have been isolated as key intermediates.     

Ovale in p-adischen Ebenen

Continuously differentiable ovals in compact disconnected Pappian planes are characterized by their finite homomorphic images.     

Acetylenic scaffolding on solid support: poly(triacetylene)-derived oligomers by Sonogashira and Cadiot-Chodkiewicz-type cross-coupling reactions

We report the first synthesis of poly(triacetylene)-derived oligomers by Pd(0)-catalysed Sonogashira and Cadiot-Chodkiewicz-type cross-coupling reactions on solid support. Oligo(phenylene triacetylene)s, members of a new class of linearly pi-conjugated oligomers with all-carbon backbones, feature very high fluorescence intensities.     

Novel extended tetrathiafulvalenes based on acetylenic spacers: synthesis and electronic properties

A selection of mono- and diacetylenic dithiafulvalenes was synthesized and employed for the construction of extended tetrathiafulvalenes (TTFs) with hexa-2,4-diyne-1,6-diylidene or deca-2,4,6,8-tetrayne-1,10-diylidene spacers between the two 1,3-dithiole rings. By stepwise acetylenic scaffolding using (E)-1,2-diethynylethene (DEE) building blocks, an extended TTF containing a total of 18 C(sp) and C(sp(2)) atoms in the spacer was prepared. The versatility of the acetylenic dithiafulvene modules was also established by the efficient synthesis of a thiophene-spaced TTF, employing a palladium-catalyzed cross-coupling reaction. The developed synthetic protocols allow functionalization of the extended TTFs in three general ways: with 1) peripheral substituents on the fulvalene cores, 2) alkynyl moieties laterally appended to the spacer, and 3) cobalt clusters involving acetylenic moieties. Strong chromophoric properties of the extended TTFs were revealed by linear and nonlinear optical spectroscopies. Extensive electrochemical studies and calculations on these compounds are also reported, as well as X-ray crystallographic analyses.     

Solid‐Phase Synthesis of Oligo(triacetylene)s and Oligo(phenylenetriacetylene)s Employing Sonogashira and Cadiot?Chodkiewicz‐Type Cross‐Coupling Reactions

We describe the first polymer‐supported synthesis of poly(triacetylene)‐derived monodisperse oligomers, utilizing Pd⁰‐catalyzed Sonogashira and Cadiot? Chodkiewicz‐type cross‐couplings as the key steps in the construction of the acetylenic scaffolds. For our investigations, Merrifield resin functionalized with a 1‐(4‐iodoaryl)triazene linker was chosen as the polymeric support ( R2 ; Figure and Scheme 3). The linker selection was made based on the results of several model studies in the liquid phase (Schemes 1 and 2). For the solid‐support synthesis of the oligo(phenylene triacetylene)s 7b – 7d , a set of only three reactions was required: i) Pd⁰‐catalyzed Sonogashira cross‐coupling, ii) Me₃Si? alkyne deprotection by protodesilylation, and iii) cleavage of the linker with liberation of the generated oligomers (Scheme 5). The longest‐wavelength absorption maxima of the oligo(phenylene triacetylene)s 7a – 7d shift bathochromically with increasing oligomeric length, from λ_max 337 nm (monomer 7a ) to 384 nm (tetramer 7d ; Table 2). Based on the electronic absorption data, the effective conjugation length (ECL) of the oligo(phenylene triacetylene)s is estimated to involve at least four monomer units and 40 C‐atoms. π‐Electron conjugation in these oligomers is less efficient than in the known oligo(triacetylene)s 14a – 14d (Table 2) due to poor transmittance of π‐electron delocalization by the phenyl rings inserted into the oligomeric backbone. Similar conclusions were drawn from the electrochemical properties of the two oligomeric series as determined by cyclic (CV) and rotating‐disk voltammetry (RDV; Table 3). In sharp contrast to 14b – 14d , the oligo(phenylene triacetylene)s 7b – 7d are strongly fluorescent, with the highest quantum yield Φ_F=0.69 measured for trimer 7c (Table 2). Whereas the Sonogashira cross‐coupling on solid support proceeded smoothly, optimal conditions for alkyne? alkyne cross‐coupling reactions employing Pd⁰‐catalyzed Cadiot? Chodkiewicz conditions still remain to be developed, despite extensive experimentation (Scheme 7 and Table 1).     

Temperature Uniformity Optimization for a silicon implant anneal into GaAs using Opus ™ simulation software

Opus ^™, which stands for “Optimized Uniformity Simulator”, has been described in the literature as a powerful tool to assist in the optimization of temperature uniformity in the STEAG Electronic Systems series of rapid thermal processors. Historically, this tool has been used extensively for a variety of silicon processing. With this simulation, the temperature uniformity of 100 mm Si₃N₄ encapsulated GaAs with a dual silicon implant anneal at 847°C, 40 s was optimized to <2°C across the wafer. Ramp rates ≤20°C/s were obtained without slip.