A novel route for tandem C−C/C−N formation via palladium-catalyzed C−H activation/styrenation and annulation of O-methylketoxime with styrenes to synthesize benzothienopyridines and benzofuropyridines has been developed. Furthermore, the intermolecular alkenylation of the ketoxime with acrylates produces 3-alkenyl O-methylketoximes in good to excellent yields. The method features mild reaction conditions and good functional group tolerance, providing a direct approach for the preparation of fused heterocycles.O ver the past decades, the directing group protocol of transition-metal-catalyzed C−H bond functionalization has become a powerful method for C−C and C−X bond formation reactions. 1 The value of this strategy achieves high regio-and stereoselectivity in terms of atom-and stepeconomic nature. As one of the most widely used protocols, the oxidative functionalizations of alkenes have attracted more attention in recent years. 2 Ortho alkenylation with the assistance of various directing groups such as carboxyl, 3 amide, 4 ester, 5 pyridine, 6 and others 7 has been extensively reported.Oxime ethers possess an excellent directing ability for C−H bond activation. 8 Previous works have demonstrated palladium-catalyzed oxime-ether-directed ortho C(sp 2 )−H functionalization, 9 such as arylation, 9a,c acylation, 9b acyloxylation, 9d,h alkoxylation, 9h and hydroxylation. 9g Aside from the above functionalized reactions, the alkenylation assisted by oxime ether has not been well explored. In 2011, Ellman and co-workers 9e reported the oxidative coupling of oxime ethers with unactivated alkenes using a cationic Rh (III) catalyst. Sun's group 9f demonstrated the ortho olefination of arylaldehyde oximes with activated olefins through a Pd(II) catalyst. More recently, Jeganmohan's group 9i described the rutheniumcatalyzed oxidant-free ortho alkenylation of aromatic amides, ketoximes, and anilides with alkenes (Scheme 1). Despite

Palladium-catalyzed direct olefination of 6-electron-withdrawing group substituted 3-arylbenzo[d]isoxazoles has been developed with exclusive site-selectivity and excellent E-stereoselectivity.

A catalytic cascade has been developed for the synthesis of biaryl‐2‐methyl acetates via a palladium‐catalyzed ortho‐C(sp2)−H bond arylation of pyruvate O‐arylmethyl ketoximes with aryl iodides followed by a solvolysis, in which the pyruvic ketoxime ester as a new auxiliary is employed to direct the C(sp2)−H bond activation. The straightforward treatment of O‐arylmethyl hydroxylamines and ethyl pyruvate with aryl iodides also provides the target products in a one‐pot fashion. Furthermore, the new palladacycle intermediate is unambiguously confirmed by single‐crystal X‐ray diffraction analysis. A plausible reaction pathway is proposed for the Pd‐catalyzed arylation‐acetolysis sequence.magnified image

A highly site-selective palladium-catalyzed ortho-mono-aroyloxylation of O-aralkyl substituted acetoxime ethers via direct Csp2–H bond activation has been developed with simple exo-acetoxime as a directing group.

A palladium-catalyzed ortho-arylation of aromatic amides ­directed by [4-chloro-2-(1H-pyrazol-1-yl)phenyl]amine as a bidentate auxiliary has been established. The reaction is characterized by normal working conditions, a broad substrate scope, and a wide functional-group tolerance. In particular, the protocol is compatible with highly sterically demanding ortho-substituted anilides and aryl iodide partners, with good yields.