Polyhalogenoaromatic compounds. Part XXXI. Synthesis and attempted cyclisation of polychlorophenyl- and polychloropyridyl-alkanols

Abstract

Several 2-polychloroarylethanols were synthesised by the reaction of polychloroaryl-lithium compounds with ethylene oxide. The products did not undergo cyclisation by intramolecular nucleophilic substitution except in the case of 2-(heptachloro-4,4′-bipyridyl-3-yl)ethanol, which gave 5,6-dichloro-2,3-dihydro-4-(tetrachloro-4-pyridyl)furo [2,3-b]pyridine.

Metal–halogen exchange between n-butyl-lithium and 2-pentachlorophenylethanol took place at the m- and p-positions. On heating, the mixture of lithiated compounds gave 4,5,6-trichloro-2,3-dihydrobenzo[b]furan via intramolecular addition to an aryne intermediate. 2-(Tetrachloro-4-pyridyl)ethanol underwent metal–halogen exchange at both positions 2 and 3 of the ring, but cyclisation was not achieved in this case.