Chiral tetradentate amine and tridentate aminocarbene ligands: Synthesis, reactivity and X-ray structural characterizations

(1R,2R)-diaminocyclohexane (1) and (1R,2R)-diaminodiphenylethylenediamine (2) were used as building blocks for the synthesis of chiral tetradentate diquinolyl-diamine and related diquinolyl-dihydroimidazolium salts. A neutral chiral palladium(II) complex was synthesized by reaction of palladium acetate with the tetradentate diquinolyl diamine derived from 2 and used as a homogeneous catalyst for the Heck reaction between styrene and haloarenes. A chiral tridentate aminocarbene was generated in situ by deprotonation of the dihydroimidazolium salt derived from 1 and allowed to react with CuI to give a new chiral quinolyl-carbene copper(I) complex.

Graphical abstractThe chiral tetradentate ligand 4 was prepared and reacted with Pd(OAc)2 to give a square planar complex in which the N–H groups are deprotonated. This complex catalyzes Heck reactions. Reaction of the deprotonated imidazolium cation 5 with CuI gives an NHC carbene complex.Figure optionsDownload full-size imageDownload as PowerPoint slide