Highly Efficient Activation of Organosilanes with η²-Aldehyde Nickel Complexes: Key for Catalytic Syntheses of Aryl-, Vinyl-, and Alkynyl-Benzoxasiloles

Abstract

An η(2)-aldehyde nickel complex was utilized as an effective activator for an organosilane in order to generate a hypervalent silicate reactant for the first time. This method was successfully applied to the highly efficient syntheses of 3-aryl-, vinyl-, and alkynyl-2,1-benzoxasiloles from benzaldehydes with aryl-, vinyl-, and alkynylsilyl groups at the ortho position. Initial mechanistic studies revealed that an intermolecular aryl transfer process was involved in the reaction mechanism. The formation of an η(2)-aldehyde complex was directly confirmed by NMR.

The Importance of Ligand‐Induced Backdonation in the Stabilization of Square Planar d10 Nickel π‐Complexes

“…We have previously reported similar high barriers to rotation with a rhodium‐olefin system . Indeed, the metallaepoxide electromer of related nickel complexes have recently been invoked by the groups of Doyle and Ogoshi based on reactivity studies, and is also shown explicitly in Group 4 complexes that display similar structural parameters to the nickel species discussed here …”

“…Experimentally,t he 31 P{ 1 H} NMR spectrum of 1 up to 110 8Cr eveals no dynamic processes, indicatingt hat the barrier to carbonyl rotation is greater than 70 kJ mol À1 .W eh ave previously reported similar high barriers to rotation with ar hodium-olefin system. [8] Indeed, the metallaepoxide electromer of related nickel complexes have recently been invoked by the groups of Doyle [42] and Ogoshi [37] based on reactivity studies, andi sa lso shown explicitly in Group 4c omplexes that display similars tructural parameters to the nickel species discussed here. [58][59][60][61][62][63] Ambiguity in the electronic structureo ft hese nickel p-complexesh inderse fforts towards the rational design of nickel-catalysed processes.…”

“…For example, we are exploring the organometallicc hemistry of nickel, [10][11][12][13][14] which has undergone ar enaissance in recent years. [15][16][17][18][19][20][21] Our focus has been the structure and reactivityo fn ickel p-complexes, which have been reported in aw ide range of catalytic processes, including the coupling of CO 2 and ethylene, [5,[22][23][24][25][26][27][28][29][30][31][32] intermolecular Tischenkoc oupling, [33][34][35] benzoxasilole synthesis, [36,37] the aldol reaction, [38] allylic alkylation, [39] allylic amination, [40] allylic amidation, [41] epoxide functionalization, [42] and Suzuki-Miyaura coupling. [43] Nickel p-complexes of heteroarenes have also been identified as key intermediates in nickel-catalysed catalystt ransfer polycondensation to form polythiophenes.…”

The importance of ligand-induced backdonation in the stabilization of square planar d10 nickel π-complexes

“…For example, we are exploring the organometallic chemistry of nickel, [10][11][12][13][14] which has undergone a renaissance in recent years. [15][16][17][18][19][20][21] Our focus has been the structure and reactivity of nickel π-complexes, which have been reported in a wide range of catalytic processes, including the coupling of CO 2 and ethylene, [5,[22][23][24][25][26][27][28][29][30][31][32] intermolecular Tischenko coupling, [33][34][35] benzoxasilole synthesis, [36,37] the aldol reaction, [38] allylic alkylation, [39] allylic amination, [40] allylic amidation, [41] epoxide functionalization, [42] and Suzuki-Miyaura coupling. [43] Nickel πcomplexes of heteroarenes have also been identified as key intermediates in nickel-catalysed catalyst transfer polycondensation to form polythiophenes.…”

Chemical etching of silicon carbide in pure water by using platinum catalyst

“…14 In general, Si can form hypervalent silicates with Lewis bases such as F À or OH À , which are considered intermediate states in a variety of chemical reactions, owing to their high nucleophilicities. [15][16][17][18][19] Therefore, OH À is considered to play the same role as F À in CARE, as shown in Fig. 1(b), and to proceed an indirect dissociative adsorption of H 2 O, i.e., an indirect hydrolysis.…”