Delocalized Carbanions. V. Tetraanion from the Lithium Reduction of cis,cis-1,2,3,4-Tetraphenylbutadiene

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The reduction of cis,cis-1,2,3,4-tetraphenylbutadiene with lithium in tetrahydrofuran yields 1,2,3,4-tetralithio-1,2,3,4-tetraphenylbutane, which upon hydrolysis with D2O gives dl and meso-1,2,3,4-tetradeuterio-1,2,3,4-tetraphenylbutane in yields up to 86%. The progress of the reduction was followed through the radical anion and dianion stages to the tetraanion by EPR and uv-visible spectroscopy. No trianion radical intermediate was detected. The tetraanion is apparently stable for weeks in the presence of excess lithium, but gradually cyclizes to give 3-benzyl-1,2,-diphenylindene upon hydrolysis, This amazing stability is attributed to a cyclic reaction scheme which regenerates tetraanion from partially protonated species. In ether, reduction with Li for 4 hr, Na for 24 hr, or K for 50 hr yielded cis- and trans-1,2,3,4-tetraphenyl-2-butene in 4:1, 5:1, and 1.4:1 ratios, respectively. Reduction for 24 hr with Li or Na for 20 days yielded 1,4-dihydro-1,2,3-triphenylnaphthalene. Reduction for 4 days with Li yielded 9,14-dihydro-9-phenyldibenz[a,c]anthracene. © 1975, American Chemical Society. All rights reserved.

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Journal of Organic Chemistry