ON THE 1,6-ADDITION OF ALKYLALUMINIUM COMPOUNDS TO para-QUINONES

Article abstract of DOI:10.1016/0022-328X(83)87156-3

Ethyl, n-butyl and i-butylaluminium dichlorides undergo 1,6-addition to a conjugated bond system O=C-C=C-C=O of para-quinones.Methylaluminium dichloride is inactive in this addition, and triethylaluminium gives low yields.The reactivities of the quinones vary with their electron affinities, and the highest yields of 1,6-addition are obtained in the reactions of chlorine derivatives of 1,4-benzoquinone.The results are discussed in terms of a radical mechanism involving a homolytic cleavage of the Al-C bond in the donor-acceptor complex formed between the reactants followed by combination of alkyl radicals and aluminium derivatives of semiquinone within a cage.The stable donor-acceptor complexes and aluminium derivative of semiquinone were isolated and characterized from the reactions of aluminium trichloride with 2,3,5,6-tetramethyl-1,4-benzoquinone and 2,3,5,6-tetrachloro-1,4-benzoquinone, respectively.