Synthesis of Benzo[<i>b</i>]siloles via KH-Promoted Cyclization of (2-Alkynylphenyl)silanes

(2-Alkynylphenyl)silanes undergo intramolecular cyclization in the presence of an excess or a subequimolar amount of potassium hydride to give a variety of new 2-substituted benzosiloles in good to excellent yields. Some of these compounds showed a high fluorescence quantum yield both in solution and in the solid state, and they also showed reversible reduction in THF

Cyclization of <i>o</i>-Allylstyrene via Hydrosilylation: Mechanistic Aspects of Hydrosilylation of Styrenes Catalyzed by Palladium−Phosphine Complexes

Hydrosilylation of o-allylstyrene with trichlorosilane in the presence of 0.3 mol % of a palladium catalyst bearing triphenylphosphine gave trans-1-methyl-2-(trichlorosilylmethyl)indan, 1-(2-(2-propenyl)phenyl)-1-trichlorosilylethane, and 1-(2-((E)-1-propenyl)phenyl)-1-trichlorosilylethane. The reaction of styrene with trichlorosilane gave a quantitative yield of 1-phenyl-1-(trichlorosilyl)ethane while allylbenzene did not give silylation products under the same reaction conditions. These results show that the hydropalladation process is operative in the hydrosilylation of styrene derivatives with trichlorosilane catalyzed by palladium−phosphine complexes

Synthesis of Benzo[<i>b</i>]siloles via KH-Promoted Cyclization of (2-Alkynylphenyl)silanes

(2-Alkynylphenyl)silanes undergo intramolecular cyclization in the presence of an excess or a subequimolar amount of potassium hydride to give a variety of new 2-substituted benzosiloles in good to excellent yields. Some of these compounds showed a high fluorescence quantum yield both in solution and in the solid state, and they also showed reversible reduction in THF

<i>a</i><i>ll-anti</i>-Octasilane: Conformation Control of Silicon Chains Using the Bicyclic Trisilane as a Building Block

The perfect all-anti-octasilane composed of two bicyclic trisilane units with trimethylsilyl groups at the termini has been synthesized. Its X-ray crystal structure and spectroscopic data demonstrate the effective σ-delocalization over the silicon framework, which is a definitive difference from the unconstrained n-Si8Me18

<i>a</i><i>ll-anti</i>-Octasilane: Conformation Control of Silicon Chains Using the Bicyclic Trisilane as a Building Block

The perfect all-anti-octasilane composed of two bicyclic trisilane units with trimethylsilyl groups at the termini has been synthesized. Its X-ray crystal structure and spectroscopic data demonstrate the effective σ-delocalization over the silicon framework, which is a definitive difference from the unconstrained n-Si8Me18

Homo- and Copolymers Based on Carbon-Bridged Oligo(<i>p</i>‑phenylenevinylene)s for Efficient Fluorescence over the Entire Visible Region

Highly efficient emissive conjugated polymers are desired for optoelectronic applications. While efficient blue to green emissive polymers have been successfully developed, efficient red emission is still challenging, mainly because of the increased nonradiative process rates upon decreasing the energy gap by extension of the π-system. Suppression of this nonradiative decay would be the key for efficient red-emitting polymers. We have previously developed carbon-bridged oligo­(<i>p</i>-phenylenevinylene)­s (COPVs), which could be promising backbones for efficient light-emitting polymers because of the suppression of rotational disorder by the rigidified coplanar structures. In this work, we report that a series of COPV-based homopolymers and copolymers show fluorescence over a wide range of the visible region (437–667 nm) with high to excellent fluorescence quantum yield: 0.60–0.94 for the blue to green emission and 0.50 for red. The polymers also exhibited high thermal and electrochemical stabilities, which could be promising for future application in optoelectronic devices

Cyclization of <i>o</i>-Allylstyrene via Hydrosilylation: Mechanistic Aspects of Hydrosilylation of Styrenes Catalyzed by Palladium−Phosphine Complexes

Hydrosilylation of o-allylstyrene with trichlorosilane in the presence of 0.3 mol % of a palladium catalyst bearing triphenylphosphine gave trans-1-methyl-2-(trichlorosilylmethyl)indan, 1-(2-(2-propenyl)phenyl)-1-trichlorosilylethane, and 1-(2-((E)-1-propenyl)phenyl)-1-trichlorosilylethane. The reaction of styrene with trichlorosilane gave a quantitative yield of 1-phenyl-1-(trichlorosilyl)ethane while allylbenzene did not give silylation products under the same reaction conditions. These results show that the hydropalladation process is operative in the hydrosilylation of styrene derivatives with trichlorosilane catalyzed by palladium−phosphine complexes

Synthesis of Tetrasubstituted Alkenes by Stereo- and Regioselective Stannyllithiation of Diarylacetylenes

Addition of trimethylstannyllithium to a diarylacetylene takes place exclusively in an anti-fashion to produce a lithio vinylstannane intermediate. The regioselectivity of the addition is controlled by the steric and electronic property of the acetylene and reaches up to >99:1. The two newly formed C−metal bonds can be sequentially and stereospecifically transformed into two new C−C bonds as illustrated by stereoselective synthesis of 4-hydroxytamoxifen and its regioisomer. A tetraarylethene bearing different aryl groups can be synthesized similarly and cyclized to a substituted dibenzo[g,p]chrysene derivative via a palladium-catalyzed arylation reaction

Modular Synthesis of 1<i>H</i>-Indenes, Dihydro-<i>s</i>-Indacene, and Diindenoindacenea Carbon-Bridged <i>p</i>-Phenylenevinylene Congener

Modular Synthesis of 1H-Indenes, Dihydro-s-Indacene, and Diindenoindacenea Carbon-Bridged p-Phenylenevinylene Congene

Preparation of 2,3-Dibromo‑1<i>H</i>‑indenes and Tetrabromodihydro‑<i>s</i>‑indacenes as Synthetic Building Blocks

The acid-induced intramolecular cyclization of 1,1-disubstituted 3-aryl-2,3-dibromoallylalcohols affords 2,3-dibromo-1H-indene derivatives. This method is also applicable to the preparation of tetrabromodihydro-s-indacenes. The thus obtained multi-brominated compounds can serve as versatile synthetic building blocks to obtain a variety of indene and indacene derivatives, as demonstrated by the synthesis of dialkylmethylene-bridged oligo(phenylenevinylene)s, which feature attractive photophysical properties