1,4-Benzoquinone, BQ
1,4-Benzoquinone is a dehydrogenation reagent. The derivative 2,3-dichloro-5,6-dicyanobenzoquinone is a stronger oxidant. Whereas the resulting phenolate as reaction product of 1,4-benzoquinone (hydroquinone) is nucleophilic, a similar oxidant - 3,3',5'5-tetra-tert-butyldiphenoquinone - can be used in the presence of sensitive electrophilic groups.
Recent Literature
A Pd(PPh3)4-catalyzed reaction between α-diazocarbonyl
compounds and arylboronic acids leads to cross-coupled products in good yields.
C. Peng, Y. Wang, J. Wang, J. Am. Chem. Soc., 2008,
130, 1566-1567.
Pd(II)-catalyzed ortho-hydroxylation of variously substituted benzoic acids
under an athmospheric pressure of oxygen or air is achieved under nonacidic
conditions. Labeling studies support a direct oxygenation of aryl C-H
bonds with molecular oxygen.
Y.-H. Zhang, J.-Q. Yu, J. Am. Chem. Soc., 2009,
131, 14654-14655.
The presence of a base stronly improves the efficiency and the selectivity of
the Pd-catalyzed oxidation of terminal alkenes in carboxylic acids. The
methodology is particularly well adapted for the oxidation of homoallylic
alcohols, for which the resulting acyloxylated products are obtained selectively
as E-isomers in good yields.
E. Thiery, C. Aouf, J. Belloy, D. Harakat, J. Le Bras, J. Muzart, J. Org. Chem., 2010,
75, 1771-1774.
1,4-Benzoquinones have been found to prevent olefin isomerization of a number
of allylic ethers and long-chain aliphatic alkenes during ruthenium-catalyzed
olefin metathesis reactions. This mild, inexpensive, and effective method
increases the overall product yield and purity.
S. H. Hong, D. P. Sander, C. W. Lee, R. H. Grubbs, J. Am. Chem. Soc.,
2005,
127, 17160-17161.
A novel chelate-controlled intermolecular oxidative Heck reaction proceeds with
a wide range of nonresonance stabilized α-olefin substrates and organoboron
reagents to afford internal olefin products in good yields and outstanding
regio- and E:Z stereoselectivities. Pd-H isomerization, common in many
Heck reactions, is not observed under these mild, oxidative conditions.
J. H. Delcamp, A. P. Brucks, M. C. White, J. Am. Chem. Soc., 2008,
130, 11270-11271.
A Pd-catalyzed intermolecular 1,2-carboamination route to indolines from N-aryl
ureas and 1,3-dienes proceeds under mild conditions in relatively nonacidic
media via a C-H insertion/carbopalladation/nucleophilic displacement process.
The in situ generation, or preformation of a palladium tosylate emerges as a key
parameter in gaining the requisite reactivity.
C. E. Houlden, C. D. Bailey, J. G. Ford, M. R. Gagné, G. C. Lloyd-Jones, K. I.
Booker-Milburn, J. Am. Chem. Soc., 2008,
130, 10066-10067.
