Nickel-Catalyzed Cross-Coupling of Aryl 2-Pyridyl Ethers with Organozinc Reagents: Removal of the Directing Group via Cleavage of the Carbon–Oxygen Bonds

Abstract

Reaction of aryl 2-pyridyl ethers with arylzinc reagents under catalysis of NiCl2(PCy3)2 affords aryl–aryl cross-coupling products via selective cleavage of CAr–OPy bonds. The reaction features a wide substrate range and good compatibility of functional groups. β-H-free alkylzinc reagents are also applicable as the nucleophiles in the transformation, whereas β-H-containing alkylzinc reagents lead to a mixture of cross-coupling and hydrogenation products.

Selective C(aryl)–O bond cleavage in biorenewable phenolics

“…In 2021, Wang reported a Ni-catalyzed Negishi-type coupling of aryloxypyridine with organozinc compounds (Scheme 28B). 152 The 2-pyridyloxy group (OPy) derived from the aryl 2-pyridyl ether, often used as a directing group in C-H bond functionalization, served as a leaving group here. Reaction of guaiacol derivative 2-(2-methoxyphenoxy)pyridine with p-toluenezinc chloride gave 69% 2-methoxy-4 0 -methyl-1,1 0biphenyl.…”

“…The bimetallic combination is essential as Ni prefers oxidative addition to the aryl tosylates while Pd oxidatively adds to the aryl triflates similar to the method reported by Weix. 155 Additional 148,[150][151][152][153] ZnCl 2 was added to modulate the transmetalation between Ni and Pd centers. 155 Interestingly, the obtained products are analogues of non-phthalate PVC plasticizer di(2-ethylhexyl)biphenyl-4-4 0 -dicarboxylate and showed comparable properties to the commonly used benchmark PVC plasticizer di(2-ethylhexyl)phthalate.…”

“…(C) Cross-electrophile coupling of C(aryl)-OH activated as a triflate. (D) Borylation of C(aryl)-OH activated as uronium salt 148,[150][151][152][153].…”