22014-22-8Relevant academic research and scientific papers
Highly efficient direct aerobic oxidative esterification of cinnamyl alcohol with alkyl alcohols catalysed by gold nanoparticles incarcerated in a nanoporous polymer matrix: A tool for investigating the role of the polymer host
Buonerba, Antonio,Noschese, Annarita,Grassi, Alfonso
, p. 5478 - 5486 (2014)
The selective aerobic oxidation of cinnamyl alcohol to cinnamaldehyde, as well as direct oxidative esterification of this alcohol with primary and secondary aliphatic alcohols, were achieved with high chemoselectivity by using gold nanoparticles supported in a nanoporous semicrystalline multi-block copolymer matrix, which consisted of syndiotactic polystyrene-co-cis-1,4- polybutadiene. The cascade reaction that leads to the alkyl cinnamates occurs through two oxidation steps: the selective oxidation of cinnamyl alcohol to cinnamaldehyde, followed by oxidation of the hemiacetal that results from the base-catalysed reaction of cinnamaldehyde with an aliphatic alcohol. The rate constants for the two steps were evaluated in the temperature range 10-45 °C. The cinnamyl alcohol oxidation is faster than the oxidative esterification of cinnamaldehyde with methanol, ethanol, 2-propanol, 1-butanol, 1-hexanol or 1-octanol. The rate constants of the latter reaction are pseudo-zero order with respect to the aliphatic alcohol and decrease as the bulkiness of the alcohol is increased. The activation energy (Ea) for the two oxidation steps was calculated for esterification of cinnamyl alcohol with 1-butanol (Ea=57.8±11.5 and 62.7±16.7 kJ mol -1 for the first and second step, respectively). The oxidative esterification of cinnamyl alcohol with 2-phenylethanol follows pseudo-first-order kinetics with respect to 2-phenylethanol and is faster than observed for other alcohols because of fast diffusion of the aromatic alcohol in the crystalline phase of the support. The kinetic investigation allowed us to assess the role of the polymer support in the determination of both high activity and selectivity in the title reaction. Golden boost to the esterification: The highly efficient and selective aerobic oxidation of cinnamyl alcohols, catalysed by gold nanoparticles supported in a nanoporous polymer matrix, in the presence of primary and secondary alkyl alcohols afforded alkyl cinnamates (see figure). The active role of the host-polymer matrix was investigated.
2-catalyzed conjugate addition of arylboronic acids to α,β-unsaturated ketones under ligand-free and neutral conditions
Zhang, Lei,Xie, Xiaomin,Fu, Lei,Zhang, Zhaoguo
, p. 3434 - 3437 (2013/06/26)
A simple and efficient Ru-catalyzed conjugate addition reaction of arylboronic acids to α,β-unsaturated ketones under neutral conditions without any additional ligands has been developed. This Ru(II)-catalytic system both fulfilled the inhibition of the β-hydride elimination in the catalytic cycle and minimized the protonolysis of arylboronic acids.
