Gold‐Nanoparticle‐Catalyzed Mild Diboration and Indirect Silaboration of Alkynes without the Use of Silylboranes

Abstract

Commercially available Au nanoparticles supported on TiO2 were used to catalyze the cis diboration of terminal and internal alkynes with bis(pinacolato)diboron. The products were obtained in excellent yields by using milder conditions, shorter reaction times, and lower catalyst loadings than those required for a heterogeneous Au nanopore catalyst. The catalytic system could be recovered and reused for five consecutive runs without any loss of activity. The combination of bis(pinacolato)diboron with the 1,2‐disilane in the presence of Au/TiO2 allowed for the σ‐bond metathesis to take place and the in situ formation of the Au nanoparticle‐tethered silylborane. Given that the Au‐catalyzed silaboration of alkynes is faster than the rates of the corresponding disilylation and diboration pathways, we were able to achieve the indirect silaboration of alkynes with good chemoselectivities (65–85 %) without the direct use of silylboranes, which are expensive and difficult to synthesize.

Gold‐Catalyzed Cross‐Coupling Reactions: An Overview of Design Strategies, Mechanistic Studies, and Applications

“…Oxidative addition of heteroatom-heteroatom bonds to heterogeneous Au catalysts for coupling reactions Gold nanoparticles can undergo oxidative addition with BÀB, SiÀSi, SiÀB, SnÀSn, CÀSn, and other bonds more readily than with stronger CÀC, CÀH, and C-halide bonds. [399][400][401][402] Jin'sgroup also utilized their methodologies based on nanoporous Au catalysis for the efficient diboration of alkynes [403] and methylenecyclopropanes. [395] They reasonedb ased on previous reports that have shown the ability of Au I for activating the SiÀSi bond, [243,245] and the hydrolysis and alcoholysis of disilanes.…”

Nanogold(0)-Catalyzed Addition of Heteroelement σ Linkages to Functional Groups

“…On the other hand, our group recently reported that commercially available Au/TiO 2 is an excellent catalyst for the diborylation of a series of terminal and internal alkynes in benzene (Scheme 26). 67 The addition occurs with a lower catalyst loading (1 mol%), under much milder conditions (65 °C) and in shorter times (2 h) compared to the AuN-Pore-catalyzed protocol. Addition of the B-B bond on AuNP, followed by cis delivery of the Au n -bound Bpin moieties to the alkyne was suggested as the most reasonable pathway.…”

“…Since silylborane is more reactive than disilane or diborane, an indirect silaboration occurs predominantly (Scheme 33). 67 In the proposed mechanism shown in Scheme 33, the initial adsorption of disilane to form PhMe 2 Si-Au n -SiMe 2 Ph was only considered for clarity, which upon reaction with pinB-Bpin forms PhMe 2 Si-Au n -Bpin via  bond metathesis. The same outcome will occur considering the initial activation of pinB-Bpin followed by reaction of the adsorbed pinB-Au n -Bpin species with PhMe 2 Si-SiMe 2 Ph.…”

Au-MOPS(3-morpholinopropane-1-sulfonic acid) coupled catalyst for the synthesis of 3-aminoalkylated indoles

“…Henceforth, coupled nanocatalyst that is Au-MOPS could be a dedicated catalyst for beneficent synthetic route to 3-amino alkylated indoles. Literally, several chemical, biochemical applications of MOPS have been found as it is an excellent buffer for many biological systems [7][8][9][10] at near-neutral pH with a pKa of 7.20. Chemical structure of MOPS contains a morpholine ring having propane sulfonic acid as a substituent at nitrogen atom.…”