Heteroaromatic ethers of phenols in nickel-catalysed ipso-replacement reactions with magnesium, zinc and tin organometallic compounds

Abstract

Phenols are readily converted in high yield into the heterocyclic ethers, 5-aryloxy-1-phenyl-1H-tetrazole, 1 and 3-aryloxy-1λ⁶,2-benzothiazole 1,1-dioxide, 2. X-Ray crystallographic analysis and other evidence shows that, in these ethers, the originally strong phenolic C–OH bond is considerably weakened on derivatization. In nickel-catalysed cross-coupling reactions with organozinc and organotin compounds, the heterocyclic parts of ethers 1,2 provide good nucleofuges. In similar cross-coupling reactions with organomagnesium halides, ethers 1 again provide good nucleofuges but, in marked contrast, ethers 2 do not. In all reactions, palladium based catalysts were mostly not effective.