In the present work, a series of α-hydroxyimine palladium complexes with bulky substituents (i.e., {[Ar-NC(R)− C(R) 2 −OH]PdCl 2 } (C1, R = Me, Ar = 2-diphenylmethyl-4,6-dimethylphenyl; C2, R = Me, Ar = 2,6-bis(diphenylmethyl)-4-methylphenyl; C3, R = Me, Ar = 2,6-bis(diphenylmethyl)-4-methyoxylphenyl; C4, R = Me, Ar = 2,6-bis(diphenylmethyl)-4-chlorophenyl; C5, R = Ph, Ar = 2,6-dimethylphenyl; C6, R = Ph, Ar = 2,6-diisopropylphenyl)) were synthesized and characterized. The structures of palladium complexes C1 and C2 were determined by X-ray diffraction. These bidentate N,O-palladium complexes were applied for direct arylation under aerobic conditions. The effects of the reaction conditions and ligand substitution on the catalytic activity were evaluated. Upon a low palladium loading of 0.5 mol %, the bulky palladium complex C6 was successfully used to catalyze the cross-coupling of a variety of five-membered heteroarenes and their benzo-condensed derivatives with (hetero)aryl bromides. The mechanistic investigation on the direct arylation supported the involvement of a Pd(0)/Pd(II) CMD process.

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Iminoamines are found to be efficient ligands for the Pd‐catalyzed Suzuki—Miyaura coupling of aryl bromides and chlorides with aryl boronic acids.

Synthesis of β-Aryl Substituted Porphyrins by Palladium-CatalyzedCross-Coupling Reactions.-β-Bromoporphyrins such as (I) undergo Suzuki cross-coupling reactions with the aryl boronic acids (II) to give the β-arylporphyrins (III) in high yield. Similarly, the analogous tetra-and octa-substituted porphyrins are obtained from the corresponding tetra-and octabromoporphyrins. The structures of these porphyrins are determined by single X-ray analysis. In contrast to the non-planar structures of octa-substituted products the tetra-β-phenyl-substituted porphyrin is centrosymmetric and shows a planar porphyrin ring. -(CHAN, K. S.; ZHOU, X.; LUO, B.; MAK, T.