Revisit of the Dessy-White intramolecular acetylene-acetylene [2 + 2] cycloadditions.
In this experiment, a series of thermal reactions of 4,4'-disubstituted 2,2'-bis(phenylethynyl)biphenyls with 2,3,4,5-tetraphenylcyclopenta-2,4-dienone were carried out under neat conditions and in diphenyl ether at temperatures between 260 and 270 degrees C to give rise to 9,10,11,12,13,14-hexaphenylcycloocta[l]phenanthrenes as the adducts in 12-23% yields. We traced these results to the intramolecular [2 + 2] thermal cyclization of 2,2'-bis(phenylethynyl)biphenyls to form 1,2-diphenylcyclobuta[l]phenanthrenes, which were further trapped as bridged-ketone Diels-Alder adducts, followed by thermal decarbonylative ring opening, which gave rise to the products.
Lee
Chung-Chieh
CC
Department of Chemistry and Institute of Polymer Science and Engineering, National Taiwan University, 1 Section 4, Roosevelt Road, Taipei 106, Taiwan.
Leung
Man-kit
MK
Lee
Gene-Hsiang
GH
Liu
Yi-Hung
YH
Peng
Shie-Ming
SM