Aromatic amine derivative type ligand

Complexes with aromatic amine derivative-type ligands 182... 

From a retrosynfhetic viewpoint, N-aryl-l,2-diimine Ni precatalysts are synthesized by (i) reaction of 1,2 diimines with nickel halides from (ii) 1,2-diimine ligands which in turn are obtained by (iii) condensing 1,2-dicarbonyl substrates with two equivalents of primary aromatic amines, usually under acidic conditions [11]. In analogy, the synthesis of N-hetaryl 1,2 diimine catalysts starts from the corresponding substituted N-heterocyclic primary amines as the amine building blocks. The synthesis of three types of such heterocycles, N-amino-pyrroles, -indoles and -carbazoles, and their corresponding diimine derivatives is presented in the following sections. 

We have been developing systematically the chemistry of Hofmann-type and related clathrate compounds. Several modifications of the metal complex host structures have been derived from that of the Hofmann-type by replacing the ammine ligands by amines or diamines, and/or the square-planar tetracyanometallate by tetrahedral one [1]. However, their structures were substantially similar to that of the Hofmann-type the volume of cavity was barely large enough to accommodate such small aromatic molecule as those enclathrated in the Hofmann-type host. 

Copper-bis oxazolidinone complex catalyzed the addition of alkyl and aromatic alkynes to the imine formed by the reaction of ethyl glyoxylate and p-anisidine, providing an easy access to chiral p,Y-alkynyl a-amino acids in good yields (61-80%) and enantioselectivities (66-74%) [38]. The presence of the two phenyl groups in the ligand was found to be crucial in the enantioselectivity enhancement and reduction of the reaction time, with aryl alkynes providing better results than alkyl acetylene derivatives [39]. Another type of Cu(II)-pybox complex led to excellent results in terms of enantioselectivities (28-93% yield, 81-98% ee) in the reaction of aliphatic alkynes with aldehydes and amines [40]. 

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