A Direct CH/ArH Coupling Approach to Oxindoles, Thio-oxindoles, 3,4-Dihydro-1 H-quinolin-2-ones, and 1,2,3,4-Tetrahydroquinolines

A copper(II)‐catalysed approach to oxindoles, thio‐oxindoles, 3,4‐dihydro‐1H‐quinolin‐2‐ones, and 1,2,3,4‐tetrahydroquinolines via formal CH, ArH coupling is described. In a new variant, copper(II) 2‐ethylhexanoate has been identified as an inexpensive and efficient catalyst for this transformation, which utilises atmospheric oxygen as the re‐oxidant. Copper(II) 2‐ethylhexanoate: The synthesis of oxindoles, thio‐oxindoles, 3,4‐dihydro‐1H‐quinolin‐2‐ones, and 1,2,3,4‐tetrahydroquinolines from linear precursors by direct CH, ArH coupling by using a single copper catalyst is reported (see scheme; DIPEA=diisopropylethylamine, EWG=electron‐withdrawing group). The cyclisations are simple to perform, run open to the air, are moisture insensitive, and use an inexpensive catalyst.