We have reported the preparation and Stille cross-coupling reaction of the first versatile organometallic reagents of azulenes, 6-(tri-
n-butylstannyl)azulenes. Synthesis and palladium-catalyzed cross-coupling reaction of 2-azulenylboronate, 2-azulenyl-4,4,5,5-tetramethyl-1,3,2-dioxaborolane were examined in order to develop a novel derivation method of azulene in a five-membered ring. 2-Azulenyl-4,4,5,5-tetramethyl-1,3,2-dioxaborolane was efficiently prepared by the reaction of 2-iodoazulenes with bis(pinacolato)diboron in the presence of palladium catalyst or the reaction of 2-azulenyllithium with trimethylborate, followed by the treatment with pinacol under acidic condition in good yields. To demonstrate the utility of 2-azulenylboronate, Miyaura-Suzuki cross-coupling reaction with
p-bromotoluene to produce 2-tolylazulene was conducted. We found the effective reaction conditions in cross-coupling of 2-azulenylboronate with aryl halides. The reactions were carried out at 80 °C by using 5 mol% of Pd
2(dba)
3, 40 mol% of P(
t-Bu)
3, and 1.5 equivalent of Cs
2CO
3. A simple synthesis of poly(2-azulenyl)benzenes, which would be key compounds for the creation of multi-step redox system stabilized by two-electron transfer, was carried out by the palladium-catalyzed reaction.
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