Resolution of β-aminophosphines with chiral cyclopalladated complexes

Abstract

Resolution of the racemic chiral b-aminophosphines Ph 2 PCH 2 CH(Ph)NH(Ar) (L 1 for Ar = C 6 H 5 and L 2 for Ar = 2,6-C 6 H 3 i Pr 2 ) has been investigated by use of different cyclopalladated complexes as chiral agents. The resulting complexes afford diastereomeric adducts in a 1:1 ratio. After successive crystallizations from ethanol, a d.e. of 98% was achieved for one aminophosphine palladium complex, while no significant d.e. was obtained after crystallizations from chlorinated solvents. The X-ray structure analysis has pointed out intermolecular hydrogen interactions N-HÁ Á ÁCl between the P,N ligand and the chloride ion, which are responsible for the formation and stabilization of the diastereomeric adducts. Thus, the use of oxygenated solvents cancels such hydrogen interactions by their stronger donor character and makes the diastereomers separation possible, allowing to isolate the optically pure (R)-Ph 2 PCH 2 CH(Ph)NH(Ph) L 1 of which the absolute configuration has been determined from the X-ray structure analysis of the related palladium dichloride complex.

Three types of reactions with intramolecular five-membered ring compounds in organic synthesis

“…(21-1), many kinds of organic compounds 21-2 are synthesized by the reaction of cyclo-metalated products 21-1 with many kinds of substrates ZXm by carbonylations, alkenylations, alkynylations, acylations, isocyanations and Diels-Alder Reactions described above. The other reactions such as transmetalations, deuterations [89], Ullmann type coupling reactions [90][91][92], C-C coupling reactions [93], halogenations [94], oxidations [95], resolutions [96][97][98], ring expansion reactions by insertion reactions of carbenes [99], the ortho-silylations of Scheme 5. Scheme 6. benzylidene amines with palladium or platinum catalysts [100,101], the asymmetric hydrogenations of dehydroamino acid derivatives [102], and asymmetric hydro phosphination reactions with chiral N,N-dimethyl-1-naphthylamine [103], are also actually utilized for many kinds of organic syntheses.…”

Synthesis, characterization and anticancer activity of new palladacycles derived from chiral α‐diimines

“…Such longstanding interest in these compounds stems from their widespread utilities, ranging from potential new applications in organic chemistry, such as catalysts,7–19 and as antitumor drugs,20–25 and the usual efforts in understanding fundamental chemistry. Among the cyclometallated complexes described, those derived from optically pure ligands26–41 have attracted additional interest, since they can be used for the resolution of mono‐ or bidentate ligands as well as in chiral discrimination processes. So far, most attention on this subject has been aimed at synthesizing novel complexes derived from a wide‐ranging assortment of functionalized ligands and we are currently focusing our efforts on the synthesis of such compounds derived from optically pure N ‐donor ligands owing to their attractive features as potential catalysts and bioactive compounds.…”