75802-19-6Relevant articles and documents
Synthesis and Photodimerization of 2- And 2,3-Disubstituted Anthracenes: Influence of Steric Interactions and London Dispersion on Diastereoselectivity
Geiger, Thomas,Haupt, Anne,Maichle-M?ssmer, C?cilia,Schrenk, Claudio,Schnepf, Andreas,Bettinger, Holger F.
, p. 10120 - 10135 (2019/08/26)
There is increased evidence that the effect of bulky groups in organic, organometallic, and inorganic chemistry is not only repulsive but can be attractive because of London dispersion interactions. The influence of the size of primary alkyl substituents in 2- and 2,3-positions of anthracenes on the diastereoselectivity (anti vs syn dimer) of the [π4s + π4s] photoinduced dimerization is investigated. The synthesis of the anthracene derivatives was achieved by Suzuki-Miyaura reaction of 2,3-dibromoanthracene with alkylboronic acids as well as by reduction of anthraquinones that were obtained from 2,3-disubstituted 1,3-butadienes and naphthoquinone followed by dehydrogenation. The mixtures of dianthracene isomers were analyzed with respect to the anti/syn-ratio of the products by X-ray crystallography and nuclear Overhauser effect spectroscopy. While for the 2,3-dimethylanthracene the anti and syn isomers were formed in equal amounts, the anti dimers are the major products in all other cases. A linear correlation (R2 = 0.98) between the steric size (Charton parameter) and the isomeric ratio suggests that the selectivity is dominated by classical repulsive steric effects. An exception is the iso-butyl substituent that produces an increased amount of the syn isomer. It is suggested that this is due to an exalted effect of London dispersion interactions.
A New Approach for Oxygenation Using Nitric Oxide under the Influence of N-Hydroxyphthalimide
Eikawa, Masahiro,Sakaguchi, Satoshi,Ishii, Yasutaka
, p. 4676 - 4679 (2007/10/03)
An approach for partial oxygenation through a carbocation as an intermediate was successfully developed by using nitric oxide under the influence of N-hydroxyphthalimide. Thus, a variety of benzylic ethers were converted into the corresponding partially oxidized compounds, which are difficult to prepare by conventional methods, in high yields. For example, the reaction of phthalane with NO in the presence of a catalytic amount of NHPI at 60°C gave phthalaldehyde in 80% yield. The reaction was found to proceed through the formation of a hemiacetal, such as 1-hydroxyphthalane. In addition, 1,3-di-tert-butoxymethyl benzene afforded 1,3-benzenedicarbaldehyde in good yield. On the other hand, isochroman was converted into 1,1′-oxodiisochromane under these reaction conditions. The reaction of ethers with NO in the presence of a NHPI catalyst is thought to proceed via the formation of a carbocation as an intermediate. A possible reaction path was suggested.
Improved Synthesis of 1-Ethoxy-1,3-dihydroisobenzofuran, a Useful Precursor to Isobenzofuran
Moss, Randall J.,Rickborn, Bruce
, p. 5391 - 5393 (2007/10/02)
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