The orthopalladation of (Z)-4-arylidene-5(4H)-oxazolones (1a-1o), with electron-withdrawing substituents (Cl, F, CF 3 ) in the 4-arylidene ring has been carried out by C-H bond activation. The process is regioselective and only the ortho C-H bond of the 4-arylidene ring is activated. The orthopalladated complexes (2a-2o) have different structures (mono-, di-and trinuclear), although the dinuclear open-book scaffold, in which the C=C bonds of the arylidene group are in a face-to-face tran- [a] Scheme 4. Different reaction pathways observed in the oxidation of 3d: synthesis of functionalized halogenated cyclobutanes 5d and 6d.

The synthesis of fused heterocycle-pyridinones has been achieved by oxidative coupling of N-unprotected primary heterocycle-amides with internal alkynes. The reaction, which is catalysed by Ru(ii) and assisted by Cu(ii), takes place through C-H and N-H bond activation of the heterocyclic unit. The scope of the reaction includes a variety of alkynes, electron-rich thiophenes, furans and pyrroles, and even electron-poor pyridines. The reaction is fully regioselective with respect to the position of the C-H bond activation due to the directing effect of the amide group. In the same way, the synthesis of fused heterocycle-pyrones (isocoumarins) has been developed by Ru-catalysed oxidative coupling of heterocyclic carboxylic acids and internal alkynes. The reaction involves C-H and O-H bond activation. This reaction also has a broad scope, from electron-rich thiophenes, furans and pyrroles to electron-deficient pyridines and quinolines.