26870-30-4Relevant academic research and scientific papers
Cobalt-Catalyzed Reductive C-O Bond Cleavage of Lignin β-O-4 Ketone Models via in Situ Generation of the Cobalt-Boryl Species
Gao, Kecheng,Xu, Man,Cai, Cheng,Ding, Yanghao,Chen, Jianhui,Liu, Bosheng,Xia, Yuanzhi
supporting information, p. 6055 - 6060 (2020/08/12)
An efficient and mild method for reductive C-O bond cleavage of lignin β-O-4 ketone models was developed to afford the corresponding ketones and phenols with PDI-CoCl2 as the precatalyst and diboron reagent as the reductant. The synthetic utility of the methodology was demonstrated by depolymerization of a polymeric model and gram-scale transformation. Mechanistic studies suggested that this transformation involves steps of carbonyl insertion, 1,2-Brook type rearrangement, β-oxygen elimination, and rate-limiting regeneration of the catalytic active Co-B species.
Facile and selective hydrogenolysis of β-O-4 linkages in lignin catalyzed by Pd-Ni bimetallic nanoparticles supported on ZrO2
Zhang, Jia-Wei,Cai, Yao,Lu, Guo-Ping,Cai, Chun
, p. 6229 - 6235 (2016/12/03)
The β-O-4 linkage in lignin can be selectively cleaved by Pd-Ni bimetallic nanoparticles supported on ZrO2 using hydrogen gas as the hydrogen donor under ambient pressure and neutral conditions. Conspicuous enhancement in activity is observed compared with single nickel and palladium catalysts based on the results of experiments and characterization. Moreover, hydrogenation of the produced phenols is tuned by adjusting the amount of NaBH4. The catalyst can be reused over ten times in the model reaction and over five times in the hydrogenolysis of lignin without an obvious change in activity and selectivity.
Chiral epoxides via borane reduction of 2-haloketones catalyzed by spiroborate ester: Application to the synthesis of optically pure 1,2-hydroxy ethers and 1,2-azido alcohols
Huang, Kun,Wang, Haiyang,Stepanenko, Viatcheslav,De Jesus, Melvin,Torruellas, Carilyn,Correa, Wildeliz,Ortiz-Marciales, Margarita
supporting information; scheme or table, p. 1883 - 1886 (2011/06/20)
An enantioselective borane-mediated reduction of a variety of 2-haloketones with 10% spiroaminoborate ester 1 as catalyst is described. By a simple basic workup of 2-halohydrins, optically active epoxides are obtained in high yield and with excellent enantiopurity (up to 99% ee). Ring-opening of oxiranes with phenoxides or sodium azide is investigated under different reaction conditions affording nonracemic 1,2-hydroxy ethers and 1,2-azido alcohols with excellent enantioselectivity (99% ee) and in good to high chemical yield. 2011 American Chemical Society.
Photochemical Generation of Radical Anions of Photolabile Aryl Ketones
Mathivanan, N.,Johnston, L. J.,Wayner, D.D.M.
, p. 8190 - 8195 (2007/10/02)
The radical anions of a series of substituted α-(aryloxy)acetophenones have been generated by trapping the solvated electron produced by 355-nm laser-induced photoionization of 4,4'-dimethoxystilbene in either acetonitrile or dimethylformamide (DMF).The radical anion of the parent ketone, α-phenoxyacetophenone, has λmax at 500 nm and decays with a rate constant 7 x 1E5 s-1.This rate constant reflects the rate of β-cleavage to generate phenoxide ion and phenylacyl radical.The rate constant for β-cleavage decreases for ketones with electron donating substituents in the α-aryloxy ring.Substituent effects on the acetophenone ring are in the opposite direction, and many of the 4-substituted (aryloxy)acetophenones have half-lives in excess of 10 μs that reflect a combination of second order processes and are not limited by β-cleavage.The generality of the photoionization/electron trapping method for the generation of radical anions of ketones with short-lived excited states that preclude direct excitation is illustrated by its application to other aryl ketones that undergo α-cleavage, β-phenyl quenching, and intramolecular hydrogen abstraction reactions.
