The regioselective generation of arynes from polyhalogenobenzenes. An improved synthesis of syn- and anti-1,4,5,8,9,12-hexahydro-1,4:5,8:9,12-triepoxytriphenylene

Abstract

The halogenated benzenes, 1,2,4,5-tetrabromobenzene 6, hexabromobenzene 9, p-dichlorotetrabromobenzene 11, and 1,2-dibromo-4,5-dichlorobenzene 12, were investigated as 1,3-bis-, 1,4-bis-, and 1,3,5-tris-aryne precursors by using alkyllithiums and alkali metal amides as the metalating reagents. The arynes were trapped in Diels-Alder reactions with furan as the diene. The title compounds 3a/b are now readily available in two steps in 7% overall yield from 1,2,4,5-tetrabromobenzene 6. © 1992.