824-69-1Relevant articles and documents
Mechanisms of hydride abstractions by quinones
Guo, Xingwei,Zipse, Hendrik,Mayr, Herbert
, p. 13863 - 13873 (2014)
The kinetics of the hydride abstractions by 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) from 13 C-H hydride donors (acyclic 1,4-dienes, cyclohexa-1,4-dienes, dihydropyridines), tributylstannane, triphenylstannane, and five borane complexes (amine-boranes, carbene-boranes) have been studied photometrically in dichloromethane solution at 20 °C. Analysis of the resulting second-order rate constants by the correlation log k2(20°C) = sN(E + N) (J. Am. Chem. Soc. 2001, 123, 9500) showed that the hydride abstractions from the C-H donors on one side and the Sn-H and B-H hydride donors on the other follow separate correlations, indicating different mechanisms for the two reaction series. The interpretation that the C-H donors transfer hydrogen to the carbonyl oxygen of DDQ while Sn-H and B-H hydride donors transfer hydride to a cyano-substituted carbon of DDQ is supported by quantum-chemical intrinsic reaction coordinate calculations and isotope labeling experiments of the reactions of D8-cyclohexa-1,4-diene, Bu3SnD, and pyridine·BD3 with 2,5-dichloro-p-benzoquinone. The second-order rate constants of the reactions of tributylstannane with different quinones correlate linearly with the electrophilicity parameters E of the quinones, which have previously been derived from the reactions of quinones with -nucleophiles. The fact that the reactions of Bu3SnH with quinones and benzhydrylium ions are on the same log k2 vs E (electrophilicity) correlation shows that both reaction series proceed by the same mechanism and illustrates the general significance of the reactivity parameters E, N, and sN for predicting rates of polar organic reactions.
Reactivity of iPrPCPIrH4 with para-benzoquinones
Wilklow-Marnell, Miles,Brennessel, William W.,Jones, William D.
, p. 209 - 214 (2017/11/24)
In the interest of investigating new hydrogen acceptors for pincer–iridium catalyzed dehydrogenations with the ability to be catalytically recycled, a series of para-benzoquinones have been reacted with iPrPCPIrH4 in various solvents and conditions. Preliminary results indicate that a wide range of quinones are capable of dehydrogenating iPrPCPIrH4, and that several turn-overs in alcohol dehydrogenation by iPrPCPIr are possible at room temperature using benzoquinone acceptors. However, strong acceptor–catalyst interactions are inhibitory toward catalysis when the acceptor is used in excess. A new class of (bis)-η2 pi-adducts, formed between iPrPCPIr and benzoquinones, nicknamed “barber-chairs”, has been identified and 3 examples have been characterized.
Diels-Alder trapping of in situ generated dienes from 3,4-dihydro-2H-pyran with p-quinone catalysed by p-toluenesulfonic acid
Mohan Raj, Radhakrishnan,Balasubramanian, Kalpattu K.,Easwaramoorthy, Deivanayagam
supporting information, p. 1115 - 1121 (2017/02/10)
This comprehensive study portrays that p-toluenesulfonic acid is a more efficient catalyst for the reaction between p-quinones and 3,4-dihydro-2H-pyran, than the Lewis acids. The products were accomplished by the Diels-Alder cycloaddition reaction and their mechanistic pathways have been formulated. The impact of C2 and C2,5 substituents of the p-quinones on the cycloaddition reaction has been explored. Remarkably, it is the first report to explore this kind of in situ generated diene for the Diels-Alder cycloaddition reaction.
