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A NiCl 2 -6H 2 O/Zn reagent with a 2-aryliminomethylpyridine ligand catalyzed cyclization/polymerization of 1,6-diynes mainly to yield the corresponding poly(1,3-butadienylene) compounds, 10 whereas, NiBr 2 -3H 2 O/Zn with use of 3-(2-(2-methoxyethoxy)-ethyl)-1-methyl-1H-imidazol-3-ium bromide as a ligand converted 1,6-diynes to the corresponding annulated 1,3,5,7-cyclooctatetraenes in a biphasic solvent system consisting of toluene and an ionic liquid. 15For homogeneous metal-catalyzed reactions, a bimetallic or bimolecular cooperative mechanism has often been proposed, where a dimerization of the metal species or dimeric interaction of the metal species plays a critical role: 1 Many cases have been postulated in which a bimetallic or bimolecular mechanism is 20 involved as a major course for effective, selective production of the desired compound. Meanwhile, the reverse case has also been reported in which dimerization of the metal species deactivates the catalyst by forming stable, coordinatively saturated, inert complexes and furthers decomposition by disproportionation. In 25 this context, isolating the catalyst to a solid phase from a solution phase by immobilization onto polymeric supports or inorganic materials is a versatile means not only for avoiding the formation of dimeric metal molecules thereby deactivating and decomposing the catalyst but also for increasing the catalyst 30 reactivity and selectivity via a bimetallic or bimolecular mechanism. 2 Herein we propose a new strategy for controling the reactions which proceed through formation of a dimeric metal intermediate: Isolation (or immobilization) of the metal-catalyst 35 into an ionic liquid (IL) 3 phase in an IL/usual organic solvent biphasic system which can separate the catalyst from the employed substrate and maintain a high catalyst concentration in the IL phase throughout the reaction, a situation which might be favorable for reactions via a dimeric metal intermediate and corresponding COTs catalyzed by a (DME)NiBr 2 /Zn [DME = 1,2-dimethoxyethane] reagent in THF-H 2 O, where reaction with a large amount of catalyst loading (20~40 mol%) realized highly selective production of COTs against co-production of [2+2+2] cycloadducts. 6 The results were rationalized by assuming the 55 dimeric mechanism that Wilke suggested.Cyclooctatetraenes (COTs) are of interest as ligands capable of coordinating to various metal atoms and electron transporting components in organic light-emitting devices, and especially as precursors for polyacetylenes in the ring-opening metathesis 60 polymerization (ROMP) reaction. 7 Efforts, therefore, have been made in developing methods for synthesizing COTs. 8 Of the existing methods, the transition metal-catalyzed [2+2+2+2] cycloaddition of alkynes can be considered one of the most attractive and direct. 65During the course of studying the transition metal-catalyzed cycloisomerization of alkynes, 9 we found that a 2-(aryliminomethyl)pyridine/NiCl 2 -6H 2 O/Zn reagent catalyzed cycloaddition of diethyl dipropargylmalo...

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