1502-05-2Relevant articles and documents
A new catalytic system for the selective aerobic oxidation of large ring cycloalkanes to ketones
Baucherel, Xavier,Arends, Isabel W. C. E.,Ellwood,Sheldon, Roger A.
, p. 426 - 428 (2003)
The combination of cobalt with N-hydroxysaccharin proved to be an effective catalyst for the aerobic oxidation of large ring cycloalkanes to the corresponding ketones.
Mehrotra,Levaprabhakara
, p. 1885 (1973)
Copper-containing SiCN precursor ceramics (Cu@SiCN) as selective hydrocarbon oxidation catalysts using air as an oxidant
Glatz, Germund,Schmalz, Thomas,Kraus, Tobias,Haarmann, Frank,Motz, Guenter,Kempe, Rhett
, p. 4231 - 4238 (2010)
A molecular approach to metal-containing ceramics and their application as selective heterogeneous oxidation catalysts is presented. The aminopyridinato copper complex [Cu2(ApTMS)2] (ApTMSH = (4-methylpyridin2-yl)trimethylsilanylamine) reacts with poly(organosilazanes) via aminopyridine elimination, as shown for the commercially available ceramic precursor HTT 1800. The reaction was studied by 1H and 13C NMR spectroscopy. The liberation of the free, protonated ligand Ap TMSH is indicative of the copper polycarbosilazane binding. Crosslinking of the copper-modified poly(organosilazane) and subsequent pyrolysis lead to the copper-containing ceramics. The copper is reduced to copper metal during the pyrolysis step up to 1000 °C, as observed by solid-state 65Cu NMR spectroscopy, SEM images, and energydispersive spectroscopy (EDS). Powder diffraction experiments verified the presence of crystalline copper. All Cu@SiCN ceramics show catalytic activity towards the oxidation of cycloalkanes using air as oxidant. The selectivity of the reaction increases with increasing copper content. The catalysts are recyclable. This study proves the feasibility of this molecular approach to metal-containing SiCN precursor ceramics by using silylaminopyridinato complexes. Furthermore, the catalytic results confirm the applicability of this new class of metal-containing ceramics as catalysts.
Complementary and selective oxidation of hydrocarbon derivatives by two cytochrome P450 enzymes of the same family
Sarkar, Md. Raihan,Bell, Stephen G.
, p. 5983 - 5995 (2020/10/08)
The cytochrome P450 enzymes CYP101B1 and CYP101C1, which are from the bacterium Novosphingobium aromaticivorans DSM12444, can hydroxylate norisoprenoids with high activity and selectivity. With the goal of expanding and establishing their substrate range with a view to developing applications, the oxidation of a selection of cyclic alkanes, ketones and alcohols was investigated. Cycloalkanes were oxidised, but both enzymes displayed moderate binding affinity and low levels of productive activity. We improved the binding and activity of these substrates with CYP101B1 by making the active site more hydrophobic by switching a histidine residue to a phenylalanine (H85F). The presence of a ketone moiety in the cycloalkane skeleton significantly improved the oxidation activity with both enzymes. CYP101C1 preferably catalysed the oxidation of cycloalkanones at the C-2 position whereas CYP101B1 oxidised these substrates with higher productivity and at positions remote from the carbonyl group. This demonstrates that the binding orientation of the cyclic ketones in the active site of each enzyme must be different. Linear ketones were also oxidised by both enzymes but with lower activity and selectivity. Cyclic substrates with an ester directing group were more efficiently oxidised by CYP101B1 than CYP101C1. Both enzymes catalysed oxidation of these esters with high regioselectively on the ring system remote from the ester directing group. CYP101C1 selectively oxidised certain terpenoid ester substrates, such as α-terpinyl and citronellyl acetate more effectively than CYP101B1. Overall, we establish that the high selectivity and activity of these enzymes could provide new biocatalytic routes to important fine chemicals.
Structure-reactivity relationship for alcohol oxidations via hydride transfer to a carbocationic oxidizing agent
Lu, Yun,Bradshaw, Joshua,Zhao, Yu,Kuester, William,Kabotso, Daniel
, p. 1172 - 1178 (2013/01/12)
Second-order rate constants were determined for the oxidation of 27 alcohols (R1R2CHOH) by a carbocationic oxidizing agent, 9-phenylxanthylium ion, in acetontrile at 60°C. Alcohols include open-chain alkyl, cycloalkyl, and unsaturated alcohols. Kinetic isotope effects for the reaction of 1-phenylethanol were determined at three H/D positions of the alcohol (KIEα-D=3.9, KIEβ-D3=1.03, KIE OD=1.10). These KIE results are consistent with those we previously reported for the 2-propanol reaction, suggesting that these reactions follow a hydride-proton sequential transfer mechanism that involves a rate-limiting formation of the α-hydroxy carbocation intermediate. Structure-reactivity relationship for alcohol oxidations was deeply discussed on the basis of the observed structural effects on the formation of the carbocationic transition state (Cδ+-OH). Efficiencies of alcohol oxidations are largely dependent upon the alcohol structures. Steric hindrance effect and ring strain relief effect win over the electronic effect in determining the rates of the oxidations of open-chain alkyl and cycloalkyl alcohols. Unhindered secondary alkyl alcohols would be selectively oxidized in the presence of primary and hindered secondary alkyl alcohols. Strained C7-C11 cycloalkyl alcohols react faster than cyclohexyl alcohol, whereas the strained C5 and C12 alcohols react slower. Aromatic alcohols would be efficiently and selectively oxidized in the presence of aliphatic alcohols of comparable steric requirements. This structure-reactivity relationship for alcohol oxidations via hydride-transfer mechanism is hoped to provide a useful guidance for the selective oxidation of certain alcohol functional groups in organic synthesis. Copyright
