Consecutive HDDA and TDDA reactions of silicon-tethered tetraynes for the synthesis of dibenzosilole-fused polycyclic compounds and their unique reactivity

Transforming Hetera-Buckybowls into Chiral Conjugated Polycycles Incorporating Epoxycyclooctadiene: a Two-Step Approach

Chiral π-conjugated polycycles have garnered increasing attention due to versatile applications in optoelectronic materials and biological sciences. In this study, we report the synthesis of chiral π-conjugated polycycles incorporating a chiral epoxycyclooctadiene moiety. Our synthetic strategy capitalizes on the novel reactions of hetera-buckybowl triselenasumanene (TSS) and is achieved in two-step manner. Firstly, the TSS is regio-selectively transformed into its ortho-quinone form. Subsequently, the nucleophilic addition reactions of TSS ortho-quinone by phenylethynides are metal ion-dependent. When utilizing (phenylethynyl)magnesium bromide as the nucleophile, two phenylethynyls are furnished onto the edged benzene ring of TSS. When the nucleophile is (phenylethynyl)lithium, a cascade of nucleophilic addition, intermolecular electron-transfer, ring-opening, and tetradehydro-Diels-Alder (TDDA) reactions occur sequentially in one-pot, ultimately affording chiral π-conjugated polycycles featuring the epoxycyclooctadiene moiety as an integral part of their backbones. This work represents a step forward in the synthesis of chiral π-conjugated polycycles using TSS as synthon.

Enantioselective Synthesis of 6/5-Spirosilafluorenes by Asymmetric Ring Expansion of 4/5-Spirosilafluorenes with Alkynes

A rhodium-catalyzed asymmetric ring expansion of 4/5-spirosilafluorenes with terminal alkynes has been developed using sterically demanding binaphthyl phosphoramidite ligand. The reaction is not only strategically distinct from cyclization or cycloaddition but also showcases the first enantioselective synthesis of axially chiral 6/5-spirosilafluorenes.

Si-containing polycyclic aromatic hydrocarbons: synthesis and opto-electronic properties

We report a straightforward synthesis of Si-containing Polycyclic Aromatic Hydrocarbons (PAHs). The impact of π-extension and exocyclic modifications on both the optical and redox properties is investigated using a joint experimental/theoretical approach. By taking advantage of the solid-state luminescence of these derivatives, electroluminescent devices are prepared. Such preliminary opto-electronic results highlight that these heteroatom-containing PAHs are promising building blocks for organic electronics.

Silicon as a powerful control element in HDDA chemistry: redirection of innate cyclization preferences, functionalizable tethers, and formal bimolecular HDDA reactions

The 1,3-diyne and diynophile in hexadehydro-Diels–Alder (HDDA) reaction substrates are typically tethered by linker units that consist of C, O, N, and/or S atoms. We describe here a new class of polyynes based on silicon-containing tethers that can be disposed of and/or functionalized subsequent to the HDDA reaction. The cyclizations are efficient, and the resulting benzoxasiloles are amenable to protodesilylation, halogenation, oxygenation, and arylation reactions. The presence of the silicon atom can also override the innate mode of cyclization in some cases, an outcome attributable to a β-silyl effect on the structure of intermediate diradicals. Overall, this strategy equates formally to an otherwise unknown, bimolecular HDDA reaction and expands the versatility of this body of aryne chemistry.

A designer silicon-containing linker enables HDDA chemistry that complements known modes of reactivity. Subsequent removal of the Si liberates a benzenoid product that is formally the result of an intermolecular HDDA reaction.

Hexadehydro-Diels-Alder Reaction: Benzyne Generation via Cycloisomerization of Tethered Triynes

The hexadehydro-Diels-Alder (HDDA) reaction is the thermal cyclization of an alkyne and a 1,3-diyne to generate a benzyne intermediate. This is then rapidly trapped, in situ, by a variety of species to yield highly functionalized benzenoid products. In contrast to nearly all other methods of aryne generation, no other reagents are required to produce an HDDA benzyne. The versatile and customizable nature of the process has attracted much attention due not only to its synthetic potential but also because of the fundamental mechanistic insights the studies often afford. The authors have attempted to provide here a comprehensive compilation of publications appearing by mid-2020 that describe experimental results of HDDA reactions.

Boron and Silicon-Substituted 1,3-Dienes and Dienophiles and Their Use in Diels-Alder Reactions

Boron and silicon-substituted 1,3-dienes and boron and silicon-substituted alkenes and alkynes have been known for years and the last 10 years have seen a number of new reports of their preparation and use in Diels-Alder reactions. This review first covers boron-substituted dienes and dienophiles and then moves on to discuss silicon-substituted dienes and dienophiles.

One-Pot Synthesis of Furo[3,4-c]indolo[2,1-a]isoquinolines through Rh(III)-Catalyzed Cascade Reactions of 2-Phenylindoles with 4-Hydroxy-2-alkynoates

An efficient and regioselective synthesis of fused polycyclic furo[3,4-c]indolo[2,1-a]isoquinolines through Rh(III)-catalyzed cascade C-H activation/annulation/lactonization of 2-arylindoles and 4-hydroxy-2-alkynoates has been developed. This cascade reaction displays high step economy and efficiency and tolerates various functional groups. The titled polycyclic furo[3,4-c]indolo[2,1-a]isoquinolines exhibit fluorescence emission.

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.