✍ Scribed by Takuya Kurahashi; Armin de Meijere
No coin nor oath required. For personal study only.
The activation of carbon-carbon s bonds under the influence of transition metals remains a fundamental challenge in organometallic chemistry. [1] Methylenecyclopropane and its derivatives were among the first substrates for which involvement of CÀC single bonds in transition-metal-catalyzed cycloaddition reactions was observed. [2] In particular, the cycloadditions of methylenecyclopropanes as a C 3 component across CÀC multiple bonds have been thoroughly investigated. [3] Surprisingly, only a limited number of transition metals such as Ni, Pd, and Pt have been explored. In recent years, cobalt complexes have been demonstrated to facilitate new types of CÀH and CÀC bond activation. [4, 5] Alper et al. as well as other groups have shown that cobalt-catalyzed carbonylative ring expansions of epoxides and aziridines are useful and efficient procedures for the synthesis of b-lactones and b-lactams, respectively. [6] In connection with our recently reported cobalt-catalyzed [5+1] cocyclization of vinylcyclopropanes with carbon monoxide leading to cyclohexenones, we found carbonylcobalt complexes to show the highest activity among the transitionmetal complexes examined. [7] In view of the observed unique reactivity of the octacarbonyldicobalt complex, we have set out to further explore carbonylative ring-expansion reactions, and here we report a novel [3+1] cocyclization of methylenecyclopropanes with carbon monoxide under cobalt catalysis.
Initially, heptylidenecyclopropane (1 a) was treated with one equivalent of octacarbonyldicobalt in THF at 50 8C for 12 h, and this led to a mixture of (2E)-and (2Z)-2heptylidenecyclobutanone (2 a) in 85 % yield (Table 1). [8] In other solvents such as toluene, dichloroethane, hexane, and acetonitrile the yields were lower. Among the carbonylmetal complexes examined, octacarbonyldicobalt gave the best
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## Abstract [PdCl(Me)(bpy)] and a mixture of the complex with cocatalysts; NaBARF (BARF = [B{C~6~H~3~(CF~3~)~2~‐3,5}~4~]^−^), NaBF~4~, AgBARF, AgBF~4~, and AgOTf, catalyze the copolymerization of 2‐phenyl‐1‐methylenecyclopropane with carbon monoxide to produce a new polyketone accompanied by ring o