Hydrosilane σ‐Adduct Intermediates in an Adaptive Zinc‐Catalyzed Cross‐dehydrocoupling of Si−H and O−H Bonds
| Autor: | Uddhav Kanbur, Arkady Ellern, Smita Patnaik, Aaron D. Sadow |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
dehydrogenative cross-coupling
sigma-adducts Silanes Full Paper 010405 organic chemistry saturation kinetics Organic Chemistry Alcohol General Chemistry Full Papers 010402 general chemistry 01 natural sciences Medicinal chemistry Catalysis Transition state 0104 chemical sciences Adduct Silyl ether zinc catalysis chemistry.chemical_compound Reaction rate constant chemistry Salt metathesis reaction silyl ethers |
| Zdroj: | Chemistry (Weinheim an Der Bergstrasse, Germany) |
| ISSN: | 1521-3765 0947-6539 |
| Popis: | 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. σ‐Silane adducts and alcohol adducts are kinetically detected intermediates in zinc‐catalyzed σ‐bond metathesis‐type dehydrocoupling reactions. These intermediates feature prominently in the reactivity of coordinatively unsaturated zinc centers, which efficiently mediate Si−O bond formation. The catalyst is responsive to reaction conditions, adapting as a function of concentration to follow the kinetically preferred mechanism. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
| Nepřihlášeným uživatelům se plný text nezobrazuje | K zobrazení výsledku je třeba se přihlásit. |