Activation of the Si–B interelement bond related to catalysis

Abstract

Covering the past seven years, this review comprehensively summarises the latest progress in the preparation and application of Si–B reagents, including the discussion of relevant reaction mechanisms.

Nickel(ii)-catalyzed reductive silylation of alkenyl methyl ethers for the synthesis of alkyl silanes

“…Our investigation was started by testing the reaction of styrene methyl ether 1a with 2, a silyl borate usually applied for silylation reactions and easily accessible in bulk quantities. 22 After careful optimization, we found a cocktail of cheap and air-stable catalyst Ni(acac) 2 (10 mol%), N-heterocyclic carbene ligand IMes·HCl (10 mol%), catalytic amount of zinc powder (20 mol%), HSiEt 3 (3 equiv.) and K 3 PO 4 (1.5 equiv.)…”

Direct Access to α‐Aminosilanes Enabled by Visible‐Light‐Mediated Multicomponent Radical Cross‐Coupling

“…We began our investigations by exploring three-component radical a-aminosilane synthesis using phenyltris(trimethylsilyl)silane 1a,m orpholine 2a and hydrocinnamaldehyde 3a as representative coupling partners.A fter careful optimization of the reaction parameters, [15] the desired aaminosilane 4a was obtained in 70 %y ield by using [Ir(dF-(CF 3 )ppy) 2 (5,bpy)]PF 6 as photocatalyst (PC, 3mol %) and HFIP as solvent under 2 45 Wb lue LED irradiation (Table 1, entry 1). With 4czlPN or [Ir(dF-(CF 3 )ppy) 2 (dtbbpy)]PF 6 in place of [Ir(dF(CF 3 )ppy) 2 (5,5'd(CF 3 )bpy)]PF 6 ,y ield of 4a decreased (Table 1, entry 2a nd 3). Solvent screening showed the importance of HFIP,since in DMF,CH 3 CN or EtOH, no conversion or only trace amount of the targeted product was observed (Table 1, entry 4-6).…”

“…Fore xample,t he Scheidt, [3] Skrydstrup [2j, 4] and Sieburth [2c,g,i] groups utilized in situ generated functionalized metallated Sinucleophiles for diastereoselective addition to C=Nb onds. However,t hese processes suffer from limitations:a )t hey require activating groups at the imine nitrogen atom and b) use air-sensitive organometallic Si-reagents which significantly restricts substrate scope.O estreich and other groups successfully prepared a-aminosilanes from imines by using air-sensitive Si-B reagents [5] through copper-catalysis. [6] An alternative disconnection strategy uses the addition of nitrogen-based reagents across vinylsilanes,w hich has been exploited by the groups of Buchwald and Miura to circumvent some of the inherent shortcomings of the Si-anion protocols.…”

Asymmetric Synthesis of Chiral 1,3‐Disubstituted Allylsilanes via Copper(I)‐Catalyzed 1,4‐Conjugate Silylation of α,β‐Unsaturated Sulfones and Subsequent Julia‐Kocienski Olefination

“…Catalytic asymmetric conjugate addition of silicon‐species to α,β‐unsaturated compounds is a highly efficient method to prepare stereogenic carbon centers containing a silyl group. [ 35 ] In 2006, Oestreich and co‐workers uncovered a Rh(I)‐catalyzed conjugate addition of PhMe 2 SiBpin [ 36‐37 ] to cyclic enones and lactones with high enantioselectivity. [ 38‐39 ] Later, the substrate scope was extended to linear ( Z )‐α,β‐unsaturated compounds with Rh(I) catalyst and ( E )‐alkenes activated by azaaryl groups with copper(I) catalyst.…”