Chemistry of siloles. The reactions of siloles with organolithium reagents

(3 + 2)-Annulation of 1,3-N,Si-tetraorganosilane reagents TsHNCH2SiBnR1R2 with arynes for efficient synthesis of 3-silaindolines

1,3-N,Si-Tetraorganosilane reagents TsHNCH2SiBnR1R2 were developed as robust synthons to prepare 3-silaindolines via a Cs2CO3-promoted (3 + 2)-annulation reaction with arynes.

Silole allylic anions instead of silanides

Reaction of a 3,4-diphenylsilole with two neopentasilanyl groups attached to the 2- and 5-positions with one equivalent of KO^tBu did not result in the expected silanide formation but yielded a silole allylic anion instead. The initially formed silanide added to a neighboring phenyl group, which then transfers a proton to the 2-position of the silole ring.

The reactions of 3,4-diphenylsiloles with two neopentasilanyl groups in 2- and 5-positions with one equivalent of KO^tBu do not yield the expected silanides but silole allylic anions instead.

Advances in Synthesis of π-Extended Benzosilole Derivatives and Their Analogs

Benzosiloles and their π-extended derivatives are present in many important advanced materials due to their excellent physical properties. Especially, they have found many potential applications in the development of novel electronic materials such as OLEDs, semiconductors and solar cells. In this review, we have summarized several main approaches to construct (di)benzosilole derivatives and (benzo)siloles fused to aromatic five- and six-membered heterocycles.

Rhodium-Catalyzed Stitching Reaction: Convergent Synthesis of Quinoidal Fused Oligosiloles

Quinoidal fused oligosiloles, a new family of silicon-bridged π-conjugated compounds, have been synthesized for the first time based on a new synthetic strategy, a stitching reaction. Multiple carbon-carbon bonds can be formed consecutively between two oligo(silylene-ethynylene)s under rhodium catalysis in a stitching manner, and up to five siloles have been fused in a quinoidal form. Physical properties of these oligosiloles have also been investigated to find a unique trend in their LUMO levels, which become higher with longer π-conjugation.

Conversion of 2-Iodobiaryls into 2,2'-Diiodobiaryls via Oxidation-Iodination Sequences: A Versatile Route to Ladder-Type Heterofluorenes

Even though 2,2'-diiodo- and 2,2'-dibromobiaryls represent accomplished precursors for heterofluorenes and other extended π-conjugated systems, their preparation still remains nontrivial when structural diversity of the biaryl backbone is required. Herein, we report a convenient method for the preparation of various 2,2'-diiodobiaryls from 2-iodobiaryls via cyclic diaryliodonium intermediates. An iodinative ring-opening of the diaryliodonium salts, mediated by a copper/diamine catalyst system, is able to afford the corresponding 2,2'-diiodobiaryls under mild conditions. The versatility of this two-step approach is demonstrated by the preparation of hitherto unexplored tetraiodoteraryls and their conversion into ladder-type π-conjugated systems.

Synthesis and NMR-study of 1-trimethylsilyl substituted silole anion [Ph₄C₄Si(SiMe₃)]⁻•[Li]⁺ and 3-silolenide 2,5-carbodianions {[Ph₄C₄Si(n-Bu)₂]⁻²•2[Li]⁺, [Ph₄C₄Si(t-Bu)₂]⁻²•2[Li]⁺} via silole dianion [Ph₄C₄Si]⁻²•2[Li]⁺

1-Trimethylsilyl, 1-R (R = Me, Et, i-Bu)-2,3,4,5-tetraphenyl-1-silacyclopentadiene [[Ph₄C₄Si(SiMe₃)]R] are synthesized from the reaction of 1-trimethylsilyl,1-lithio-2,3,4,5-tetraphenyl-1-silacyclopentadienide anion [[Ph₄C₄Si(SiMe₃]⁻•[Li]⁺ (3) with methyl iodide, ethyl iodide, and i-butyl bromide. The versatile intermediate 3 is prepared by hemisilylation of the silole dianion [Ph₄C₄Si]⁻²•2[Li]⁺ (2) with trimethylsilyl chloride and characterized by ¹H-, ¹³C-, and ²⁹Si-NMR spectroscopy. 1,1-bis(R)-2,3,4,5-tetraphenyl-1-silacyclopentadiene [Ph₄C₄SiR₂] {R = n-Bu (7); t-Bu (8)} are synthesized from the reaction of 2 with n-butyl bromide and t-butyl bromide. Reduction of 7 and 8 with lithium under sonication gives the respective 3-silolenide 2,5-carbodianions {[Ph₄C₄Si(n-Bu)₂]⁻²•2[Li]⁺ (10) and {[Ph₄C₄Si(t-Bu)₂]⁻²•2[Li]⁺ (11)}, which are characterized by ¹H-, ¹³C-, and ²⁹Si-NMR spectroscopy. Polarization of phenyl groups in 3 is compared with those of silole anion/dianion, germole anion/dianion, and 3-silolenide 2,5-carbodianions 10 and 11.

Synthesis of silafluorenes by iridium-catalyzed [2 + 2 + 2] cycloaddition of silicon-bridged diynes with alkynes

[reaction: see text] Silicon-bridged 1,6-diynes underwent [2 + 2 + 2] cycloaddition with alkynes in the presence of an iridium(I)-phosphine catalyst to afford densely substituted silafluorene derivatives. Extended silafluorene skeletons were constructed by the [2 + 2 + 2] cycloaddition of tetraynes.

Electronic Structure and Stability of Pentaorganosilicates

The exceptional stability of recently reported pentaorganosilicates is investigated by bond energy analyses. Experimental coupling constants are used to probe their electronic structure, entailing bonds with mixed ionic-covalent character. Our analyses reconfirm that the axial bonds are more prone to heterolytic cleavage than are the equatorial bonds. Aryl substituents provide substantial electronic stabilization by charge delocalization, but cause steric crowding due to ortho-hydrogen repulsion. In contrast, silicates with two ax,eq biaryl groups are not congested. The remaining substituent is confined to an equatorial site, where it is insensitive to elimination. These concepts adequately explain the experimentally observed stability trends and are valuable for designing other stable pentaorganosilicates.

Poly(9,9-dialkyl-3,6-dibenzosilole)—a high energy gap host for phosphorescent light emitting devices

The preparation of the 3,6-disubstituted dibenzosilole monomers , and by two different routes is described; Suzuki copolymerisation afforded poly(9,9-dioctyl-3,6-dibenzosilole) which has a sufficiently high triplet energy (2.55 eV) to function as a host for green electrophosphorescent emitters.