A new approach to the construction of radialenes by the nickel-catalyzed cyclooligomerization of [3]cumulenes (butatrienes)

Abstract

The zero-valent nickel complexes, which are generated in situ from nickel(I1) complexes by reduction with zinc, have been found to catalyze the cyclooligomerization of butatrienes, 2,3-dihalo-1,3-butadienes, 1,4-dichloro-2-butyne, and 1,l-dibromoethylene to give the corresponding [4]-and [6]radialenes. The formation of the [4]-and (6lradialenes depends on the reaction conditions, especially on solvent, and each product of the reactions can be prepared selectively. This method provides access to the synthesis of novel derivatives of radialenes of theoretical and synthetic interest. The spectral and chemical data indicate the highly symmetrical structure of radialenes Radialenes (polymethylenecycloalkanes) have received considerable attention from both theorists and experimentalists'-" because of their particular arrangement of r-electrons and because of advances in the understanding of their potentials as electron donor and acceptor for organic metals5 and ferromagnetic organic compounds.6 Of the parent radialenes, [ 3]-2 and [4]radialene3 (1 and 2) were reported two decades ago. However, [5]radialene 0002-7863/88/1510-8494$01.50/0 I , , 0 1988 American Chemical Society Nickel-Catalyzed Radialene ConstructionScheme I11

Synthesis of Vinylcycloheptadienes by the Nickel-Catalyzed Three-Component [3 + 2 + 2] Cocyclization. Application to the Synthesis of Polycyclic Compounds

“…Compound 6a was synthesized in 62% yield when the reaction was carried out on a 5 mmol scale, and the Ni(PPh 3 ) 2 Br 2 -PPh 3 -Zn catalytic system was used (entry 2). 17b, 21 The cycloheptadiene 6b was also isolated in good yield when the reaction of 1, 2b, and 5 was executed (entry 3). The reaction of 1, 2c, and 5 proceeded in moderate yield to afford 6c (entry 4).…”

Molecules with Linear π‐Conjugated Pathways between All Substituents: Omniconjugation

“…These molecules possess an uninterrupted cyclic arrangement of exocyclic double bonds. [27,28] Of special interest are compounds based on [3]radialenes (see model 4 in Fig. 1).…”

Thermal cyclotrimerization of tetraphenyl[5]cumulene(tetraphenylhexapentaene) to a tricyclodecadiene derivative

“…3 Although the cyclooligomerizations of ethylenes, acetylenes, allenes and butatrienes have been widely investigated, 4 only few examples are known of cyclotrimerization of cumulenes. Early studies showed that allenes trimerize at 130-200 1C in benzene to give isomeric cyclic trimers, 5 and butatrienes afford [6]radialenes upon transition metal catalyzed cyclotrimerization. 6 However, no reports are known for the trimerization of hexapentaenes, except for the oxidative cyclotrimerization of hexapentaene-extended quinocumulene.…”

“…Early studies showed that allenes trimerize at 130-200 1C in benzene to give isomeric cyclic trimers, 5 and butatrienes afford [6]radialenes upon transition metal catalyzed cyclotrimerization. 6 However, no reports are known for the trimerization of hexapentaenes, except for the oxidative cyclotrimerization of hexapentaene-extended quinocumulene. 7 In a broader sense, thermal reactions of higher cumulenes have been studied only in limited cases, presumably due to instability of these highly unsaturated compounds in atmospheric oxygen.…”