Ligandless Regioselective Hydrosilylation of Allenes Catalyzed by Gold Nanoparticles

Abstract

The first example of Au-catalyzed hydrosilylation of allenes is presented using recyclable gold nanoparticles as catalyst, without the requirement of any external ligands or additives. The hydrosilane addition takes place on the more substituted double bond of terminal allenes in a highly regioselective manner. The observed regioselectivity/reactivity modes are attributed to steric and electronic factors.

Supported Au Nanoparticles‐Catalyzed Regioselective Dehydrogenative Disilylation of Allenes by Dihydrosilane

“…Continuing our exploration on the unconventional reactivity of dihydrosilanes in Au 0 ‐catalyzed transformations, we explored their reactivity against allenes. Previously we had shown that simple monohydrosilanes react smoothly with allenes in the presence of Au/TiO 2 yielding hydrosilylation products, primarily or exclusively on the more substituted double bond of terminal allenes (Scheme ) . In this paper we report that the reaction between a dihydrosilane (Et 2 SiH 2 ) and a series of allenes mainly yields products of dehydrogenative disilylation exclusively on the terminal double bond, in contrast to regioselectivity pattern of the analogous hydrosilylation reaction (Scheme ).…”

“…Previously we had shown that simple monohydrosilanes react smoothly with allenes in the presence of Au/TiO 2 yieldingh ydrosilylation products, primarily or exclusively on the more substituted double bond of terminal allenes (Scheme1). [9] In this paper we report that the reactionb etweenadihydrosilane (Et 2 SiH 2 )a nd as eries of allenesm ainly yields products of dehydrogenative disilyl-ation exclusively on the terminal double bond, in contrast to regioselectivity pattern of the analogous hydrosilylation reaction (Scheme 1). Thus, mixingE t 2 SiH 2 (2.5 equiv) with am onosubstituted or an 1,1-disubstituted allene and Au/TiO 2 (1 % mol) as catalyst, in anhydrous benzene at 25 8C, resultst ot he predominant formation of the dehydrogenatedd isilylation adducts with concomitantH 2 elimination ( Table 1).…”

Hydrosilylation of Allenes Over Palladium–Gold Alloy Catalysts: Enhancing Activity and Switching Selectivity by the Incorporation of Palladium into Gold Nanoparticles

“…In this supported catalysis, the determining factor for both the reaction efficiency and the product selectivity is the reactivity of the surface hydride and allyl species. Stratakis et al experimentally proved that allyl species on Au NPs exhibited a carbocationic character . From these facts, striking effects of the incorporation of Pd atom into Au NPs on drastic enhancement of catalytic activity and change of product selectivity are based on the formation of highly nucleophilic hydride species on Pd atoms, which in turn facilitates C–H coupling with cationic σ‐allyl species on Au atoms ( A ) to provide internal alkenylsilanes.…”

“…In fact, previous studies have demonstrated the selective formation of allylsilanes by Pd‐ Co‐ or Mo‐catalyzed hydrosilylation involving protonation of the allene center carbon (Scheme a and 1b). Despite the fact that allene hydrosilylation under Ni, Pd, Al and Au catalysis has emerged as an effective route to terminal alkenylsilanes (Scheme c), an synthetic route to internal alkenylsilanes via allene hydrosilylation has scarcely been explored (Scheme d).…”

A Bithiophene‐Promoted ppm Levels of Palladium‐Catalyzed Regioselective Hydrosilylation of Terminal Allenes

“…Hence, the development of new and efficient methods for the synthesis of versatile allylsilanes has been paid more and more attention. The hydrosilylation of allenes is one of the most straightforward and atom‐economical approaches to prepare such compound, which has been achieved with various metal catalysts, such as Mo, Co, Ni, Pd and Au . However, controling the regio‐ and stereoselectivity is still challenging in this reaction, as up to six potential isomeric products can be generated (Figure a).…”