Synthesis of Substituted Linear Ter- and Quaterphenyls via Dewar Benzenes

Abstract

Tetramethylcyclobutadiene-AlCl₃ complex reacted with bisalkynes possessing phenylene and biphenylene spacer giving rise to mono- and bis-Dewar benzenes. The rearrangement of the bis-Dewar benzene derivatives under thermal conditions (150 ˚C) yielded the corresponding linear ter- and quaterphenyl compounds possessing substituted terminal benzene rings. A mixture of an alkynylbiphenyl and a terphenyl was also obtained by the reaction of tetramethylzirconacyclopentadiene with bisalkynylbenzene in 13% combined yield.

Dewar benzene - alkynes - cyclobutadiene - polycycles - metallacycles

References and Notes

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10a

Dimethyl 3,3′′,4,4′′,5,5′′,6,6′′-octamethyl-1,1′:4′,1′′-terphenyl-2,2′′-dicarboxylate (7a)
^¹H NMR (600 MHz, CDCl₃, Me₄Si): δ = 2.02 (s, 6 H), 2.25-2.29 (m, 18 H), 3.43 (s, 3 H), 3.56 (s, 3 H), 7.17-7.18 (m, 4 H). ^¹³C NMR (150 MHz, CDCl₃, Me₄Si): δ = 16.22, 16.25, 16.75, 17.50, 17.53, 17.55, 17.78, 51.38, 51.59, 129.07, 129.13, 129.42, 132.04, 132.10, 132.76, 133.00, 134.59, 134.69, 136.12, 136.32, 136.55, 136.69, 138.79, 138.96, 170.82, 170.91. IR (CHCl₃): ν = 2962, 2923, 2852, 1725, 1263, 1099, 1018, 801 cm^-¹. MS (EI): m/z (%) = 459 (12) [M⁺], 458 (41), 427 (30), 426 (100), 395 (23), 379 (22), 351 (12), 295 (22). HRMS: m/z calcd for C₃₀H₃₄O₄: 458.2457; found: 458.2439. R _f = 0.65 (hexane-EtOAc = 1:1).

10b

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