Reactivity of the 1-hydropyrenyl anion towards α,ω-dibromoalkanes

Abstract

The reactivity of the 1-hydropyrenyl mono-anion (1^–) towards 1,2-dibromoethane, 1,3-dibromopropane and 1,4-dibromobutane has been examined. Six novel products were isolated from these reactions and characterised: spiro[cyclopropane-1,5′-(1′,5′-dihydropyrene)](2), 1,3a-dihydro-1,3a-ethanopyrene (3), 9,10,11,11a-tetrahydro-8bH-cyclopenta[e]pyrene (4), 2,3,3a,12a-tetrahydro-1H-cyclopenta[c]pyrene (5), 3a-(3-bromopropyl)-3,3a-dihydropyrene (6) and 8b,9,10,11,12,12a-hexahydrobenzo[e]pyrene (7). The formation of these products could be rationalised by initial attack of the dibromoalkane at positions 3a and 5 of 1^–. Deprotonation of the initial ω-bromoalkyldihydropyrenes leads to intramolecular alkylation, the course of which depends on the length of the alkyl chain. Attempts to aromatize the products resulted, except in the case of 5, in the fully aromatic pyrene derivatives cyclopenta[cd]pyrene, benzo[e]pyrene, pyrene and the new cyclopenta-fused pyrene derivative, 10,11-dihydro-9H cyclopenta[e]pyrene (9).