Reductive Ring Opening of N-Benzoylaziridine by Anthracene Hydride (Anion of 9,10-Dihydroanthracene) via Base-Induced Fragmentation of the Intermediate Carbonyl Adduct

Article abstract of DOI:10.1021/jo00268a021

As previously reported reaction of anthracene hydride (AH^-) or of its oxa analogue xanthenyl anion (X^-), with N-benzoylaziridines 1a,b can result in amidoethylation (2a,b and 3a,b) of the carboanion, in reductive opening (4a,b) of the aziridine ring, and in attack on the carbonyl group of 1a,b.We now show with 1a that both the rate of ring opening and the amount of reductive opening are significantly enhanced by an excess of AH^-Li⁺ while the initially formed (90percent) carbonyl adduct 6a survives with a defict of AH^-Li⁺.Both effects due to carbanion excess are absent with X^-Li⁺ but are much stronger with AH^-Na⁺.These results point to a rapid process that is triggered off by deprotonation at position 10 of the carbonyl adduct 6.A concerted or subsequent homolytic fragmentation is proposed to generate the ketyl 5 of 1, followed by homolytic ring opening of 5 to yield the radical 12, which is reduced to the carbanion 14.The latter forms 4 by capturing a proton from dihydroantracene.Inaccessibility of reductive ring opening for a trialkylacetyl-activated aziridine is demonstrated again (18).