CH<sub>3</sub>···O Hydrogen Bond. Implications of Its Presence from the Substituent Effects on the Populations of Rotamers in 4-Substituted 9-Ethyl-1-methoxytriptycenes and 9-(Substituted Phenoxymethyl)-1,4-dimethyltriptycenes
作者:Yoshio Tamura、Gaku Yamamoto、Michinori Oki
DOI:10.1246/bcsj.60.1781
日期:1987.5
In the series of 4-substituted 9-ethyl-1-methoxytriptycenes, the populations of the sc conformer increase as the electron-density on the 1-methoxy–oxygen decreases. This trend was interpreted on the basis of steric repulsion which should increase as the electron density on the oxygen atom becomes high. In contrast, in the series of 9-(substituted phenoxymethyl)-1,4-dimethyltriptycenes, the high electron density on the aryloxy–oxygen favors the sc form. The stabilization of the sc form relative to the ap in the high electron density compounds in the latter series is attributed to the presence of CH3···O hydrogen bond, since other factors like Coulombic interactions, van der Waals repulsions, and van der Waals attractions could be excluded from being the main factor for the stabilization.
Restricted Rotation Involving the Tetrahedral Carbon. XXXVI. Stereodynamics of 9-(2-MethylbenzyI)triptycene Derivatives
作者:Gaku Yamamoto、Michinori Oki
DOI:10.1246/bcsj.54.481
日期:1981.2
DNMR study of a series of singly peri-substituted 9-(2-methylbenzyl)triptycene derivatives showed that the interconversion among the ap and ±sc rotamers with the o-methyl group pointing outside the triptycyl skeleton occurs by two consecutive gear motion steps by way of the unstable rotamers with the o-methyl group pointing inside. The+sc\ightleftharpoons−sc interconversion barriers (13.2—14.1 kcal/mol) are lower than the ap\ightleftharpoons±sc ones (17.7–20.8 kcal/ mol). The aryl group passes over a peri-hydrogen at the transition state of the former process and over the peri-substituent in the latter.
Reduction of 1-substituted anthraquinones to 1- and 4-substituted anthrones
作者:V. A. Loskutov
DOI:10.1007/bf02494377
日期:1997.2
The regioselectivity of reduction of 1-substituted anthraquinones to 1- or 4-substituted anthrones is determined by both the nature of the substituent and the type of the reducing system used.
Examining Heterodimerization by Aryl C–N Coupling in Dynemicin Biosynthesis
作者:Paramita Pal、Jamie R. Alley、Craig A. Townsend
DOI:10.1021/acschembio.2c00709
日期:2023.2.17
two halves by an aryl C–Nbond is examined here using a variety of experimental approaches. We demonstrate that this heterodimerization is specific for anthracenyl iodide as the corresponding bromo- and amino-substituted anthracenes do not support dynemicin biosynthesis. Furthermore, biochemical experiments and chemical model reactions support an SRN1 mechanism for the aryl C–N coupling in which electron