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.

[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.

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

Trifunctional incompletely condensed polyhedral oligomeric silsesquioxanes (RSiMe2O)3R'7Si7O9 (IC-POSSs) are considered as intriguing building nanoblocks dedicated to constructing highly advanced organic-inorganic molecules and polymers. Up to now, they have been mainly obtained via hydrosilylation of olefins, while the hydrosilylation of the C≡C bonds has not been studied at all, despite the enormous potential of this approach resulting from the possibility of introducing 3, 6, or even more functional groups into the IC-POSS structure. Therefore, in this work, we present a highly selective and efficient synthesis of the first example of tripodal alkenyl-functionalized IC-POSSs, obtained via platinum-catalyzed hydrosilylation of the terminal and internal alkynes, as well as symmetrically and nonsymmetrically 1,4-disubstituted buta-1,3-diynes with silsesquioxanes (HSiMe2O)3R'7Si7O9 (R' = i-C4H9 (1a), (H3C)3CH2C(H3C)HCH2C (1b)). The resulting products are synthetic intermediates that contain C═C bonds and functional groups (e.g., OSiMe3, SiR3, Br, F, B(O(C(CH3)2)2 (Bpin)), thienyl), which make them suitable for application in the synthesis of novel, complex, hybrid materials with unique properties.

Application of Green Solvents: PEG and scCO2 in the Mono- or Biphasic Catalytic Systems for the Repetitive Batch Coupling of Vinylsilanes with Vinyl Boronates toward 1-Boryl-1-silylethenes.

A new method for the repetitive batch silylative coupling (trans-silylation) of vinylsilanes with vinyl boronates in the presence of Ru(CO)Cl(H)(PCy3)2 immobilized in poly(ethylene glycols) (PEGs) has been developed. Three PEGs (PEG600, PEG2000, and MPEG2000) with different molecular weights and end groups (MW = 600-2000) were tested as solvents and immobilization media, while an aliphatic solvent (n-hexane or n-heptane) or supercritical CO2 was used for product extraction. By applying 2 mol % of the Ru-H catalyst, it was possible to carry out up to 15 complete runs, with the predominant formation of 1-boryl-1-silylethenes. This immobilization strategy permitted for catalyst reuse and obtaining higher TON values (approximately 660-734) compared to the reaction in conventional solvents (∼50). Detailed kinetic studies of the most effective catalytic system were performed to determine catalyst activity and stability. Moreover, the reactions were carried out in an MPEG2000/scCO2 biphasic system, positively influencing the process sustainability.

Pt-Catalyzed Hydrosilylation of 1,3-Diynes with Triorganosilanes: Regio- and Stereoselective Synthesis of Mono- or Bis-silylated Adducts.

An efficient method has been successfully developed for the functionalization of various 1,3-diynes by the hydrosilylation reaction with triethyl- or triphenylsilane catalyzed by Pt catalysts (Pt2(dvs)3, PtO2, or Pt(PPh3)4). Comprehensive optimization studies were performed for the first time to find suitable process conditions for the stereo- and regioselective formation of mono- or bis-silylated adducts from commercially available substrates and catalysts. Silyl-substituted 1,3-enynes or bis-silyl-functionalized buta-1,3-dienes were obtained with excellent yields and fully characterized.

Recent Advances in Boron-Substituted 1,3-Dienes Chemistry: Synthesis and Application.

In the syntheses developed to access naturally occurring compounds, especially bioactive substances, boron-functionalized dienes (also "linchpin" reagents) are used as key reagents. Structurally unique dienes are found in nature, and play important biological and chemical roles. Recently, linchpin moieties have been proved as useful substrates for a variety of highly functionalized chemical transformations. The products of these processes are potentially of some use for the syntheses of an important class of natural products showing a wide range of biological activities. This review describes progress in the synthesis of borylsubstituted buta-1,3-dienes as well as their application in organic chemistry.

A stereoselective synthesis of (E)- or (Z)-ß-arylvinyl halides via a borylative coupling/halodeborylation protocol.

A new stereoselective method for the synthesis of (E)-ß-arylvinyl iodides and (E)- or (Z)-ß-arylvinyl bromides from styrenes and vinyl boronates on the basis of a one-pot procedure via borylative coupling/halodeborylation is reported. Depending on the halogenating agent as well as the mode of the halodeborylation reaction, (E) or (Z) isomers are selectively formed.

Magnetically Recyclable Borane Lewis Acid Catalyst for Hydrosilylation of Imines and Reductive Amination of Carbonyls.

Fluorinated arylborane-based Lewis acid catalysts have shown remarkable activity and serve as ideal examples of transition metal-free catalysts for diverse organic transformations. However, their homogeneous nature poses challenges in terms of recyclability and separation from reaction mixtures. This work presents an efficient technique for the heterogenization of boron Lewis acid catalysts by anchoring Piers' borane to allyl-functionalized iron oxide. This catalyst demonstrates excellent activity in the hydrosilylation of imines and the reductive amination of carbonyls using various silanes as reducing agents under mild reaction conditions. The catalyst exhibits broad tolerance towards a wide range of functional substrates. Furthermore, it exhibits good recyclability and can be easily separated from the products using an external magnetic field. This work represents a significant advance in the development of sustainable heterogenous metal-free catalysts for organic transformations.

Preparation of T8 and double-decker silsesquioxane-based Janus-type molecules: molecular modeling and DFT insights.

We present a methodology for the synthesis of inorganic-organic Janus-type molecules based on mono-T8 and difunctionalized double-decker silsesquioxanes (DDSQs) via hydrosilylation reactions, achieving exceptionally high yields and selectivities. The synthesized compounds were extensively characterized using various spectroscopic techniques, and their sizes and spatial arrangements were predicted through molecular modelling and density functional theory (DFT) calculations. Quantum chemical calculations were employed to examine the interactions among four molecules of the synthesized compounds. These computational results allowed us to determine the propensity for molecular aggregation, identify the functional groups involved in these interactions, and understand the changes in interatomic distances during aggregation. Understanding the aggregation behaviour of silsesquioxane molecules is crucial for tailoring their properties for specific applications, such as nanocomposites, surface coatings, drug delivery systems, and catalysts. Through a combination of experimental and computational approaches, this study provides valuable insights into the design and optimization of silsesquioxane-based Janus-type molecules for enhanced performance across various fields.

Selective synthesis of boron-substituted enynes via a one-pot diboration/protodeboration sequence.

An efficient and facile one-pot protocol to access enynylboronates via a Pt-catalyzed diboration/protodeboration strategy has been developed. The reaction is suitable for various silylsubstituted symmetrical and unsymmetrical 1,3-diynes, leading to π-conjugated organoboron compounds with excellent regio- and stereoselectivity.

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.

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.

Reactivity of a series of triaryl borates, B(OArx)3, in hydroboration catalysis.

In this paper, we compare the reactivity of a series of triaryl borates B(OArx)3 as catalysts for the hydroboration of alkenes and alkynes. It was observed that commercially available B(OPh)3 performed the poorest, whereas catalysts with o-F atoms appeared to perform much better.

Directed cis-hydrosilylation of borylalkynes to borylsilylalkenes.

Hydrosilylation of borylalkynes to borylsilylalkenes (with a different arrangement of substituents) has been successfully developed. The cis-addition of SiH group to the CC bonds was directed by using a specific catalyst. The obtained products are crucial synthons for the introduction of the CC bonds in organic synthesis.

Synthesis of bifunctional disiloxanes via subsequent hydrosilylation of alkenes and alkynes.

The first protocol for the synthesis of unsymmetrical bifunctional 1,1,3,3-tetramethyldisiloxane derivatives via subsequent hydrosilylation of alkenes and alkynes is presented. The methodology described has vast functional group tolerance and is extremely efficient towards the formation of novel disiloxane-based building blocks.

New catalytic route to borasiloxanes.

A new, highly selective method for effective synthesis of boryl silyl ethers (borasiloxanes) via O-borylation of silanols with vinylboronates catalyzed by the Ru-H complexes [RuHCl(CO)(PCy3)2] and [RuHCl(CO)(PPh3)3] is described.

Selective Hydrosilylation of Alkynes with Octaspherosilicate (HSiMe2 O)8 Si8 O12.

Comprehensive studies on platinum-catalyzed hydrosilylation of a wide range of terminal and internal alkynes with spherosilicate (HSiMe2 O)8 Si8 O12 (1 a) were performed. The influence of the reaction parameters and the types of reagents and catalysts on the efficiency of the process, which enabled the creation of a versatile and selective method to synthesize olefin octafunctionalized octaspherosilicates, was studied in detail. Within this work, twenty novel 1,2-(E)-disubstituted and 1,1,2-(E)-trisubstituted alkenyl-octaspherosilicates (3 a-m, 6 n-t) were selectively obtained with high yields, and fully characterized (1 H, 13 C, 29 Si NMR, FTIR, MALDI TOF or TOF MS ES+ analysis). Moreover, the molecular structure of the compound (Me3 Si(H)C=C(H)SiMe2 O)8 Si8 O12 (3 a) was determined by X-ray crystallography for the first time. The developed procedures are the first that allow selective hydrosilylation of terminal silyl, germyl, aryl, and alkyl alkynes with 1 a, as well as the direct introduction of sixteen functional groups into the 1 a structure by the hydrosilylation of internal alkynes. This method constituted a powerful tool for the synthesis of hyperbranched compounds with a Si-O based cubic core. The resulting products, owing to their unique structure and physicochemical properties, are considered novel, multifunctional, hybrid, and nanometric building blocks, intended for the synthesis of star-shaped molecules or macromolecules, as well as nanofillers and polymer modifiers. In the presented syntheses, commercially available reagents and catalysts were used, so these methods can be easily repeated, rapidly scaled up, and widely applied.

(E)-9-(2-iodovinyl)-9H-carbazole: a new coupling reagent for the synthesis of π-conjugated carbazoles.

The one-pot synthesis of (E)-9-(2-iodovinyl)-9H-carbazole via sequential ruthenium-catalyzed silylative coupling of N-vinylcarbazole with vinyltrimethylsilane and iododesilylation is reported. Its use as a new building block in the palladium-catalyzed Sonogashira and Suzuki-Miyaura coupling reactions to yield new carbazole-containing (E)-but-1-en-3-ynes and (E,E)-buta-1,3-dienes is demonstrated.

A new catalytic route to boryl- and borylsilyl-substituted buta-1,3-dienes.

Vinyl-substituted boronates in the presence of complexes containing Ru-H bonds (preferably [Ru(CO)ClH(PCy(3))(2)], Cy: cyclohexyl) react regioselectively with terminal ethynes (involving silylethynes), albeit with the exception of phenylacetylene, to produce boryl- and borylsilyl-substituted buta-1,3-dienes with a preference for E,E-diene. The reaction opens a new catalytic route for the preparation of dienylboronates, and particularly dienylsilylboronates, that are functionalised building blocks in the synthesis of organic and natural products. The mechanism of this new reaction was proved to involve an insertion of alkyne into Ru-H bonds followed by an insertion of coordinated vinyl boronate into the Ru-C= bond and beta-hydrogen transfer to the metal to eliminate boryldiene or borylsilyldiene.