Transition metal catalysed ipso-replacement reactions of heteroaromatic phenolic ethers by zinc and tin organometallic compounds
作者:Amadeu F. Brigas、Robert A. W. Johnstone
DOI:10.1039/c39940001923
日期:——
Highly crystalline tetrazolyl or pseudo-saccharyl O-ethers of phenols provide good, selective leaving groups for nickel- and palladium-catalysed cross-coupling reactions with organo-zinc and -tin compounds to give a C–C bond in place of the original phenolic C–O bond.
Heteroaromatic ethers of phenols in nickel-catalysed ipso-replacement reactions with magnesium, zinc and tin organometallic compounds
作者:Amadeu F. Brigas、Robert A. W. Johnstone
DOI:10.1039/b001333l
日期:——
Phenols are readily converted in high yield into the heterocyclic ethers, 5-aryloxy-1-phenyl-1H-tetrazole, 1 and 3-aryloxy-1λ6,2-benzothiazole 1,1-dioxide, 2. X-Ray crystallographic analysis and other evidence shows that, in these ethers, the originally strong phenolic C–OH bond is considerably weakened on derivatization. In nickel-catalysed cross-coupling reactions with organozinc and organotin compounds, the heterocyclic parts of ethers 1,2 provide good nucleofuges. In similar cross-coupling reactions with organomagnesium halides, ethers 1 again provide good nucleofuges but, in marked contrast, ethers 2 do not. In all reactions, palladium based catalysts were mostly not effective.
Metal-Assisted Reactions. Part XXX. Control of Rates of Heterogeneously Catalyzed Transfer Hydrogenolysis through Changes in Solvent Composition
作者:José A. C. Alves、Amadeu F. Brigas、Robert A. W. Johnstone
DOI:10.1071/ch02252
日期:——
suitable for a heterogeneously catalyzed reaction in the liquid-phase. Solubility in any chosen solvent is also important. As examples, rates of heterogeneously catalyzed liquid-phase transfer hydrogenolyzes of aryl tetrazolyl ethers (1) have been shown to be highly dependent on both the nature of the solvent and on the solution concentrations of the reactants. The rate of reaction can be varied from
Mechanisms in heterogeneous liquid-phase catalytic-transfer reduction: the importance of hydrogen-donor concentration
作者:Amadeu F. Brigas、Robert A. W. Johnstone
DOI:10.1039/c39910001041
日期:——
In liquid-phase heterogeneous catalytic-transfer reduction, the concentration of hydrogen donor is of extreme importance, being able to suppress reaction entirely if it is not kept very low relative to the concentration of the reducible substrate; biphasic solvent systems provide a simple means of exercising the required control.