Polyhalogenation-Facilitated Spirolactonization at the <i>meta</i>-Position of Phenols

A novel dearomative spirolactonization/polyhalogenation of phenols that employs hypervalent iodine PhICl2 (iodobenzene dichloride) as both an oxidant and chlorine source with an indispensable base, or only using NBS (N-bromosuccinimide) without any additives, is presented. Halide participations are a vital factor in the cascade reaction of 3′-hydroxy-[1,1′-biphenyl]-2-carboxylic acids with good selectivities and reactivities and induced the rapid constructions of multiple C–halogen bonds and directional CO bonds in a one-step operation under mild conditions. In gaining a good understanding of the mechanism, the increase in number of bromine atoms was inferred rationally from the spirolactonization process, assisted by DFT calculations and high-resolution mass spectrometry. Mechanistic experiments suggest that the formation of a stable carbocation intermediate plays a great role in the migration of oxygen to spirolactonization

Copper-Catalyzed Oxidative Difunctionalization of Terminal Unactivated Alkenes

The copper­(II)-promoted free-radical oxidative difunctionalization of terminal alkenes to access ketoazides by utilizing molecular oxygen has been reported. A series of styrene derivatives have been evaluated and were found to be compatible to give the desired difunctionalized products in moderate to good yields. The role of molecular oxygen both as an oxidant and oxygen atom source in this catalytic transformation has been unquestionably demonstrated by ¹⁸O-labeling studies and a radical mechanistic pathway involving the oxidative formation of azidyl radicals is also designed. This environment-friendly catalytic oxidative protocol can transform aldehyde to nitrile