6863-58-7Relevant articles and documents
Novel Si(II)+and Ge(II)+Compounds as Efficient Catalysts in Organosilicon Chemistry: Siloxane Coupling Reaction ?
Fritz-Langhals, Elke,Kneissl, Sotirios,Piroutek, Phillip,Werge, Sven
, (2020/09/02)
Novel catalytically active cationic Si(II) and Ge(II) compounds were synthesized and isolated in pure form. The Ge(II)+-based compounds proved to be stable against air and moisture and therefore can be handled very easily. All compounds efficiently catalyze the oxidative coupling of hydrosil(ox)anes with aldehydes and ketones as oxidation reagents and simultaneously the reductive ether coupling at very low amounts of 0.01 mol %. Because the catalysts also catalyze the reversible cyclotrimerization of aldehydes, paraldehyde can be used as a convenient source for acetaldehyde in siloxane coupling. It is shown that the reaction is especially suitable to make siloxane copolymers. Moreover, a new fluorine-free weakly coordinating boronate anion, B(SiCl3)4-, was successfully combined with the Si(II) and Ge(II) cations to give the stable catalytically active ion pairs Cp*Si:+B(SiCl3)4-, Cp*Ge:+B(SiCl3)4-, and [Cp(SiMe3)3Ge:+]B(SiCl3)4-.
Cobalt-Catalyzed Secondary Alkylation of Arenes and Olefins with Alkyl Ethers through the Cleavage of C(sp2)-H and C(sp3)-O Bonds
Dong, Xunqing,Li, Qun,Li, Guigen,Lu, Hongjian
, p. 13402 - 13413 (2018/11/20)
A novel cobalt-catalyzed C-H alkylation of arenes and olefins is achieved with (pyridin-2-yl)isopropyl amine as an N,N-bidentate directing group. Different linear, branched, and cyclic alkyl ethers were used as practical secondary alkylating reagents through cleavage of C(sp3)-O bond, providing an efficient approach to the synthesis of verstile o-alkylated arylamides and tetrasubstituted acrylamides. Mechanistic studies indicate that cleavage of the inert C(sp3)-O bond involves a cobalt-promoted radical process and that cleavage of the inert C(sp2)-H bond by a cobalt catalyst is a rate-limiting step.
Influence of butanol isomers on the reactivity of cellulose towards the synthesis of butyl levulinates catalyzed by liquid and solid acid catalysts
Démolis, Alexandre,Eternot, Marion,Essayem, Nadine,Rataboul, Franck
, p. 3747 - 3754 (2016/05/09)
Butyl esters of levulinic acid form an interesting class of bio-based compounds that can be used, for example, as fuel additives. Their preparation mainly proceeds through the esterification of levulinic acid while the few reported studies on their direct synthesis from cellulose give limited information. In the present work, we studied for the first time in detail the influence of butanol isomers on the non-catalyzed cellulose liquefaction and the acid catalyzed formation of butyl levulinates from cellulose. In the absence of catalysts there was no influence of the alcohol class on liquefaction which reached 70-85% after 2 hours at 300 °C. In the presence of catalysts, we showed that the class of the alcohol had a significant influence on the butyl levulinate yield. With primary alcohols yields of 50% were obtained in the presence of H2SO4 (200 °C, 30 min). This level of yield can be considered as very interesting for these kinds of one-pot transformations involving cellulose. With secondary alcohols, yields less than 20% were obtained while no butyl levulinate was formed with tertiary alcohols. We also report for the first time this transformation in the presence of solid acids. Insoluble Cs2HPW12O40 or sulfated zirconia catalyzed the reaction heterogeneously despite deactivation leading to limited yields of 13% (200 °C, 1 hour). We finally show that water in butanol had an ambivalent role in enhancing the cellulose reactivity but limiting the esterification step and found that 5-7 wt%/butanol of water was the optimum amount.
