Alkenyl-Functionalized Open-Cage Silsesquioxanes (RSiMe2O)3R'7Si7O9: A Novel Class of Building Nanoblocks

Pt(PPh3)4 and Pt(PPh3)4@IL catalyzed hydroboration of ketones

An efficient method for the reduction of various ketones via [Pt(PPh3)4]-catalyzed hydroboration with HBpin has been successfully developed for the first time. The protocol is suitable for symmetrical and unsymmetrical derivatives possessing electron donating or withdrawing functional groups. O-borylated products were easily converted to 2° alcohols via hydrolysis with high isolated yields. According to the low-temperature NMR spectroscopy, a reaction mechanism was proposed. Additionally, effective immobilization of the catalyst in the ionic liquid [BMIM][NTf2] was applied to increase the productivity of the process by carrying out reactions under the repetitive batch mode, obtaining higher TON values and limiting the amount of expensive Pt used. The catalyst stability and almost neglectable leaching were confirmed by ICP-MS analysis of the extracted mixture. A simple separation method via extraction with n-heptane, efficient catalyst immobilization, and the commercial availability of the Pt complex, make this protocol an attractive method for the hydroboration of ketones.

Functionalization of octaspherosilicate (HSiMe2O)8Si8O12 with buta-1,3-diynes by hydrosilylation

Hydrosilylation with octaspherosilicate (HSiMe2O)8Si8O12 (1) has provided hundreds of molecular and macromolecular systems so far, making this method the most popular in the synthesis of siloxane-based, nanometric, cubic, and reactive building blocks. However, there are no reports on its selective reaction with 1,3-diynes, which allows for the formation of new products with unique properties. Therefore, herein we present an efficient protocol for monohydrosilylation of symmetrically and non-symmetrically 1,4-disubstituted buta-1,3-diynes with 1. The compounds obtained bear double and triple bonds and other functionalities (e.g., Br, F, OH, SiR3), making them highly desirable, giant building blocks in organic synthesis and material chemistry. These compounds were fully characterized by 1H, 13C, 29Si, 1D NOE, 1H-13C HSQC NMR, FT-IR, and MALDI TOF MS, EA, UV-Vis, and TGA analysis. The TGA proved their high thermal stability up to 427 ℃ (Td10%) for compound 3j.

Synthesis of unsymmetrically and symmetrically functionalized disiloxanes via subsequent hydrosilylation of C≡C bonds

A selective synthesis of unsymmetrically functionalized disiloxanes via the subsequent hydrosilylation of internal alkynes in the first step, and alkynes (terminal or internal) or 1,3-diynes in the second, with 1,1,3,3-tetramethyldisiloxane (1) is presented for the first time. Using developed approaches performed in a stepwise or one-pot manner a new family of disubstituted disiloxanes was obtained which had previously been inaccessible by other synthetic methods. Moreover, symmetrically functionalized disiloxanes were obtained by direct hydrosilylation of 2 equivalents of terminal or internal alkynes with 1, showing the unique versatility of the hydrosilylation process. Three examples of symmetric disiloxanes were characterized by single crystal X-ray diffraction for the first time. As a result, a wide group of new compounds which can find potential applications as building blocks or coupling agents was obtained and characterized.

Slick Synthetic Approach to Various Fluoroalkyl Silsesquioxanes-Assessment of their Dielectric Properties

We present a smart and efficient methodology for the synthesis of a variety of fluorinated silsesquioxanes (SQs) with diverse Si-O-Si core architecture. The protocol is based on an easy-to-handle and selective hydrosilylation reaction. An investigation on the placement of the reactive Si-HC=CH₂ vs. Si-H in the silsesquioxane, as well as silane vs. olefin structure, respectively, on the progress and selectivity of the hydrosilylation process, was studied. Two alternative synthetic pathways for obtaining a variety of fluorine-functionalized silsesquioxanes were developed. As a result, a series of mono- and octa- T₈ SQs, tri- 'open-cage' T₇ SQs, in addition to di- and tetrafunctionalized double-decker silsesquioxane (DDSQ) derivatives, were obtained selectively with high yields. All products were characterized by spectroscopic (NMR, FTIR) techniques. Selected samples were subjected to the measurements revealing their dielectric permittivity in a wide range of temperatures (from -100 °C to 100 °C) and electric field frequencies (10⁰-10⁶ Hz).

[Pt(PPh3)4]-Catalyzed Selective Diboration of Symmetrical and Unsymmetrical 1,3-Diynes

A straightforward, efficient, and selective method for the preparation of novel boryl-functionalized enynes or dienes via [Pt(PPh₃)₄]-catalyzed diboration of a broad spectrum of symmetrical and unsymmetrical 1,3-diynes was developed. The catalytic cycle of diboration was proposed on the basis of low-temperature ³¹P NMR studies. An alternative isolation method via product condensation on a cold finger was developed, which, in contrast to previous literature reports, eliminates the need for the additional transformation of rapidly decomposing enynyl pinacol boronates to more stable silica-based column chromatography derivatives during the separation step. To prove the efficiency of this simple catalytic protocol, bisboryl-functionalized enynes were synthesized in a gram scale and tested as useful building blocks in advanced organic transformations, such as hydrosilylation and Suzuki and sila-Sonogashira couplings. The presence of silyl, boryl, as well as other functions like halogen or alkoxy in their structures builds a new class of multifunctionalized enynes that might be modified in various chemical reactions.

Hydroelementation of diynes

This review highlights the hydroelementation reactions of conjugated and separated diynes, which depending on the process conditions, catalytic system, as well as the type of reagents, leads to the formation of various products: enynes, dienes, allenes, polymers, or cyclic compounds. The presence of two triple bonds in the diyne structure makes these compounds important reagents but selective product formation is often difficult owing to problems associated with maintaining appropriate reaction regio- and stereoselectivity. Herein we review this topic to gain knowledge on the reactivity of diynes and to systematise the range of information relating to their use in hydroelementation reactions. The review is divided according to the addition of the E-H (E = Mg, B, Al, Si, Ge, Sn, N, P, O, S, Se, Te) bond to the triple bond(s) in the diyne, as well as to the type of the reagent used, and the product formed. Not only are the hydroelementation reactions comprehensively discussed, but the synthetic potential of the obtained products is also presented. The majority of published research is included within this review, illustrating the potential as well as limitations of these processes, with the intent to showcase the power of these transformations and the obtained products in synthesis and materials chemistry.

Directed cis-hydrosilylation of borylalkynes to borylsilylalkenes

Directed by the choice of catalyst cis-hydrosilylation of borylalkynes leads to novel borylsilylalkenes which are crucial synthons for the introduction of the carbon–carbon double bonds in organic synthesis.

Cobalt-Catalyzed Dehydrogenative C-H Silylation of Alkynylsilanes

Herein, we report that a cobalt catalyst permits the general synthesis of substituted alkynylsilanes through dehydrogenative coupling of alkynylsilanes and hydrosilanes. Several silylated alkynes, including di‐ and trisubstituted ones, were prepared in a one‐step procedure. Thirty‐seven compounds were synthesized for the first time by applying our catalyst system. The alkynylsilanes bearing hydrosilyl moieties provide an opportunity for further functionalization (e. g., hydrosilylation). The use of primary silanes as substrates and precatalyst activators permits the use of inexpensive and easily accessible 3d metal precatalysts, and avoids the presence of additional activators.