Abstract
Three‐coordinate PhBOXMe2 ZnR (PhBOXMe2 =phenyl‐(4,4‐dimethyl‐oxazolinato; R=Me: 2 a, Et: 2 b) catalyzes the dehydrocoupling of primary or secondary silanes and alcohols to give silyl ethers and hydrogen, with high turnover numbers (TON; up to 107) under solvent‐free conditions. Primary and secondary silanes react with small, medium, and large alcohols to give various degrees of substitution, from mono‐ to tri‐alkoxylation, whereas tri‐substituted silanes do not react with MeOH under these conditions. The effect of coordinative unsaturation on the behavior of the Zn catalyst is revealed through a dramatic variation of both rate law and experimental rate constants, which depend on the concentrations of both the alcohol and hydrosilane reactants. That is, the catalyst adapts its mechanism to access the most facile and efficient conversion. In particular, either alcohol or hydrosilane binds to the open coordination site on the PhBOXMe2 ZnOR catalyst to form a PhBOXMe2 ZnOR(HOR) complex under one set of conditions or an unprecedented σ‐adduct PhBOXMe2 ZnOR(H−SiR′3) under other conditions. Saturation kinetics provide evidence for the latter species, in support of the hypothesis that σ‐bond metathesis reactions involving four‐centered electrocyclic 2σ–2σ transition states are preceded by σ‐adducts.
Highlights
Silicon-oxygen bond formation has wide-ranging impact in synthetic applications, ranging from the construction of organic-inorganic hybrid materials[1,2,3] to the assembly of complex molecules.[4]
Saturation kinetics provide evidence for the latter species, in support of the hypothesis that σ-bond metathesis reactions involving four-centered electrocyclic 2σ–2σ transition states are preceded by σ-adducts
Silyl ethers themselves have important roles in cross-coupling,[5] as templates for cyclization,[6] as protecting groups,[7,8] and even improving the efficacy of medicinal compounds.[9,10]. These moieties are conventionally formed from alcohols and chlorosilanes; this approach, is hindered by the formation of HCl or salts as by-products, moisture sensitivity and competing hydrolysis of chlorosilanes, as well as the limited reactivity of bulky tertiary alcohols and bulky chlorosilanes,[11] incompatibilities with base-sensitive groups,[12,13] and difficulties selecting for a desired stoichiometry needed to assemble multiple components into synthesisenabling scaffolds
Summary
Silicon-oxygen bond formation has wide-ranging impact in synthetic applications, ranging from the construction of organic-inorganic hybrid materials[1,2,3] to the assembly of complex molecules.[4]. The effect of coordinative unsaturation on the behavior of the Zn catalyst is revealed through a dramatic variation of both rate law and experimental rate constants, which depend on the concentrations of both the alcohol and silane reactants.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
