A palladium-catalyzed decarbonylative/decarboxylative [4 + 2] annulation of phthalic anhydrides with cyclic diaryliodonium salts to synthesize triphenylenes has been developed. The reaction shows good functional group tolerance with high yield...

C–H annulations at N- and C2-aryls of an imidazole have been well researched, while the annulation on C4(5)-aryls especially the reactivity and site-selectivity among these aryls remain unknown. Herein, a...

Selective C–H activation of a molecule containing multiple directing groups is an important but challenging issue in organic chemistry. Herein, a combined directing group (hydrazone-oxime) selectively directed [4 + 2] annulation cascade to synthesize novel 1,1′-biisoquinoline mono-N-oxides has been developed. Owing to the subtle differences in electronic properties between hydrazone and oxime, the first C–H annulation with alkynes preferentially occurs at the hydrazone side to form 1-oximido isoquinolines, which then undergoes a second C–H annulation with iodonium ylides at the oxime side. The two [4 + 2] annulations work smoothly under redox-neutral conditions and can be performed in one pot, without utilization of stoichiometric external oxidants. Moreover, ESI-MS and DFT calculations have been conducted to corroborate the reaction mechanism. Such novel biisoquinoline skeletons can pave the way for future research prospects with synthetic value.

An efficient one-pot synthesis of 1,1′-biisoquinolines by a three-component reaction of commercially available raw materials (benzils, NH4OAc, and alkynes) is disclosed. This complicated reaction involves in situ diimine formation via benzil-NH4OAc condensation, Rh(III)-catalyzed 2-fold imine-directed C–H activation, and annulation with alkynes. Both symmetric and unsymmetric 1,1′-biisoquinolines could be assembled in moderate to high yields. The reaction mechanism is supported through ESI-MS, in which Cp*ClRh+, Cp*(OAc)Rh+, Cp*(OPiv)Rh+, and two rhodacycle intermediates are successfully detected to explain the evolution of rhodium species.