Reactions of lithium phenylacetylenide and lithium 3,3-dimethylbut-1-ynide with 3,6-di-tert-butyl-1,2-benzoquinone.: Molecular structure of 2,5-di-tert- butyl-8-(3,6-di-tert-butyl-1,2-binzoquinon-4-yl)-8-phenylocta-2,4,6,7-tetraen-1,6-olide

Reactions of 3,6-di-tert-butyl-1,2-benzoquinone with PhC=CLi and (BuC)-C-t=CLi are multistage processes. In;the first stage, nucleophilic 1,2-addition of the organometallic compound to o-benzoquinone occurs to form the corresponding hydroxycyclohexadienone derivative. In polar solvents, the latter undergoes rearrangement through insertion of the oxygen atom into the ring to form a new allenic organolithium compound. The reaction of the newly formed organometallic compound with the initial o-quinone occurs either as a one-electron transfer to yield lithium semiquinolate and a dimerization product; viz., 4,4'-bi(2,5-di-tert-butyl-9,9-dimethyldeca-2,5-dien-7-yn-1,6-olide), or as the 1,4-addition to yield 2,5-di-tert-butyl-8-(3,6-di-tert-butyl-1,2-benzoquinon-4-yl)-8-phenylocta-2,4,6,7- tetraen-1,6-olide. The structure of the latter compound was established by X-ray diffraction analysis and by NMR and IR spectroscopy.