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

Abstract

In recent years, supported Au nanoparticles and nanoporous Au materials have shown remarkable catalytic activity in the activation of σ heteroelement linkages such as, Si–H, Si–Si, B–B and B–Si, and their subsequent addition to functional groups, primarily π bonds. In this review article we discuss the reaction modes known to date, and attempt to discuss the mechanistic clues of these transformations which are rather unexpected in terms of conventional transition-metal catalysis concepts, given that the catalytic sites are metallic Au(0).1 Introduction2 Activation of Hydrosilanes2.1 Reactions of Hydrosilanes with Alkynes2.1.1 Hydrosilylation2.1.2 Dehydrogenative Coupling2.2 Reactions of Hydrosilanes with Allenes2.3 Reactions of Hydrosilanes with Carbonyl Compounds and Imines2.4 Reactions of Hydrosilanes with α-Diazo Carbonyl Compounds2.5 Miscellaneous Transformations from the Nano Au-Catalyzed Activation­ of Hydrosilanes3 Activation of Disilanes3.1 Disilylation of Alkynes3.2 Reactions of 1,1,2,2-Tetramethyldisilane with Alkynes4 Activation of Diboranes4.1 Diborylation of Alkenes4.2 Diborylation of Alkynes4.3 Diborylation of Allenes4.4 Diborylation of Methylenecyclopropanes5 Activation of Silylboranes5.1 Silaboration of Alkynes5.2 Silaboration of Allenes5.3 Silaboration of Unactivated Epoxides and Oxetanes5.4 Reactions of Silylboranes with Aromatic Carbonyl Compounds6 Conclusions and Future Perspectives

Reduction of the Diazo Functionality of α-Diazocarbonyl Compounds into a Methylene Group by NH3BH3 or NaBH4 Catalyzed by Au Nanoparticles

“…Amine borane IV reduces a second molecule of α-diazocarbonyl compound through a similar catalytic cycle on Au n , and it is transformed into NH 2 BH(OMe) 2 , which finally undergoes a third Au n -catalyzed reduction round. The final fate of ammonia borane is its transformation into NH 4 B(OMe) 4 [25], which is proved by 11 B NMR (see Supplementary Materials). Similarly, the final fate of NaBH 4 is the formation of the analogous salt NaB(OMe) 4 , which resonates at about 3 ppm [26] in 11 B NMR (see Supplementary Materials).…”

“…While no reaction occurs in a series of dry apro vents (dichloromethane, diethyl ether, hexane, or benzene), to our pleasure, we fou the treatment of 1a with NH3BH3 (0.4 molar equivalent) or NaBH4 (0.3 molar equi in MeOH for 15 min at room temperature resulted in the quantitative formation reduced product 3a (Scheme 2). In the absence of Au/TiO2 or in the presence of the s Over the past two decades, supported Au nanoparticles (Au NPs) and other nano Au(0) materials have attracted significant attention due to their surprising ability to catalyze a plethora of organic transformations, despite the metallic character of Au atoms on nanoparticles [10][11][12][13], including transfer hydrogenation reductive processes [14,15]. Given the heterogeneous nature of Au NP-catalyzed processes and that they can be easily recycled and reused on the vast majority of the reported protocols, they can be considered as benign green catalysts.…”

“…Over the past two decades, supported Au nanoparticles (Au NPs) and other nano Au(0) materials have attracted significant attention due to their surprising ability to catalyze a plethora of organic transformations, despite the metallic character of Au atoms on nanoparticles [ 10 , 11 , 12 , 13 ], including transfer hydrogenation reductive processes [ 14 , 15 ]. Given the heterogeneous nature of Au NP-catalyzed processes and that they can be easily recycled and reused on the vast majority of the reported protocols, they can be considered as benign green catalysts.…”

β-Borylation of conjugated carbonyl compounds with silylborane or bis(pinacolato)diboron catalyzed by Au nanoparticles

“…1 Among them, the activation and subsequent addition of interelement σ bond linkages (Si-H, Si-Si, B-B, B-Si) to alkynes, allenes and even strained σ systems represent a practical route for the synthesis of synthetically attractive organosilicon and organoboron compounds. 2 Our group was the first to establish the ability of supported Au NPs to smoothly activate the Si-B bond of the fairly stable Me 2 PhSiBpin (pin: pinacolato) in its reaction with alkynes. 3 Since then, a range of applications appeared using this silylborane and Au/TiO 2 as the catalyst.…”

Au Nanoparticle‐Catalyzed Silaboration of Aryl‐Substituted Cyclopropyl Aldehydes Forming Rearranged β‐Boronate Silyl Enol Ethers

“…More recently we have presented its Au/TiO 2 ‐catalyzed reaction with aromatic aldehydes and acetophenones which results to a C–C bond forming pathway, instead . The activation of pinB‐SiMe 2 Ph on Au/TiO 2 most probably involves the chemisorption of the interelement Si‐B linkage on the electron deficient low‐coordinated Au atoms, primarily at the corners of the Au nanoparticle, and then follows the delivery of the two chemisorbed partners on the proximal physisorbed substrate . While pinB‐SiMe 2 Ph adds to alkynes, allenes, epoxides and oxetanes,, in the case of carbonyl compounds, a silylative pinacol‐type reductive dimerization pathway is exclusively observed (Scheme ).…”