Synthesis of Substituted 2,2′‐Bipyridines and 2,2′:6′,2′′‐Terpyridines by Cobalt‐Catalyzed Cycloaddition Reactions of Nitriles and α,ω‐Diynes with Exclusive Regioselectivity
reactions exhibiting exclusive regioselectivity. Thus, symmetrical and unsymmetrical 1,6-diynes and 2-cyanopyridine reacted in the presence of 5 mol % of dppe, 5 mol % of CoCl2⋅6 H2O and 10 mol % of zinc powder to provide the corresponding 2,2′-bipyridines. Under identical reaction conditions, 1-(2-pyridyl)-1,6-diynes and nitriles reacted smoothly with exclusive regioselectivity to produce 2,2′-bipyridines
Regioselective Syntheses of Substituted Pyridines and 2,2′-Bipyridines by Cobalt-Catalyzed [2+2+2] Cycloaddition of α,ω-Diynes with Nitriles
作者:Sentaro Okamoto、Yu-ki Sugiyama
DOI:10.1055/s-0030-1260068
日期:2011.7
2-bis(diphenylphosphino)ethane-cobalt(II) chloride-zinc catalyst in 1-methylpyrrolidin-2-one at room temperature to 50 ˚C, α,ω-diynes reacted with nitriles by a [2+2+2] cycloaddition pathway to give annulated pyridines or 2,2′-bipyridines. The regioselectivity of the reaction is controlled by a combination of steric and electronic effects. The reaction of diynes with a terminal trimethylsilyl group gave the