Scheme 1. Hydroxylation of C sp 2ÀH bonds. BQ = benzoquinone, DG = directing group.

A Pd-catalyzed aerobic oxidative C–H nitration and acylation of arenes with simple and readily available tert-butyl nitrite (TBN) and toluene as the radical precursors has been developed. Molecular oxygen is employed as the terminal oxidant and oxygen source to initiate the active radical reactants. Many different directing groups such as pyridine, pyrimidine, pyrazole, pyridol, pyridylketone, oxime, and azo groups can be employed in these novel transformations. The PdII/PdIV catalytic cycle through a radical process is the most likely pathway for these oxidative C–H nitration and acylation reactions.

No abstract

The aerobic direct dehydrogenative annulation of N-iminopyridinium ylides with terminal alkynes leading to pyrazolo[1,5-a]pyridine derivatives has been developed.

Sanfte „Verbrennung“: Die Titelreaktion gelingt durch eine Kombination aus übergangsmetallkatalysierter C‐H‐Aktivierung und einem NHPI‐initiierten Radikalprozess. Die neutralen Bedingungen und das ideale Oxidationsmittel, molekularer Sauerstoff, machen diese Hydroxylierung zu einem umweltschonenden und praktischen Prozess. NHPI=N‐Hydroxyphthalimid.