Oxygenated phenanthrenes via quinol ketals: Cyclization vs. migration
摘要:
2-methoxyphenanthrenes were prepared by reaction of lithiated 2-bromostyrenes with quinone monoketals followed by acid-mediated cyclization of the resulting p-arylquinol ketals. Substitution at the bromostyrene side-chain or the quinone monoketal ring had only a modest effect on yields, but oxygen substitution on the bromostyrene aromatic nucleus resulted in a competing 1,2-aryl migration arising during the quinol ketal cyclization step. The extent of this rearrangement was found to be a function of the Lewis acid/solvent system employed.
The stereoselectivity of the formation of macrocyclicstilbenes as well as the regioselectivity of their photocyclization are strongly influenced by the length of the connecting alkanediyl chain. The stereoisomers of the macrocyclicstilbenes and the corresponding diols are identified by chemical and spectroscopic means.
Regiocontrolled Synthesis of Ethene-Bridged<i>para</i>-Phenylene Oligomers Based on Pt<sup>II</sup>- and Ru<sup>II</sup>-Catalyzed Aromatization
作者:Tse-An Chen、Te-Ju Lee、Ming-Yuan Lin、Shariar M. A. Sohel、Eric Wei-Guang Diau、Shie-Fu Lush、Rai-Shung Liu
DOI:10.1002/chem.200902231
日期:2010.2.8
We report the regiocontrolled syntheses of ethene‐bridged para‐phenylene oligomers in three distinct classes by using PtII‐ and RuII‐catalyzed aromatization. This synthetic approach has been developed based on twofold aromatization of the 1‐aryl‐2‐alkynylbenzene functionality, which proceeds by distinct regioselectivity for platinum and ruthenium catalysts. Variable‐temperature NMR spectra provide