Synthesis, structure, and reactivity of new chiral ferrocenyl pyrazole ligands

New chiral ferrocene-based ligands containing an N-phenyl substituted pyrazole unit directly attached to a Cp ring were prepared starting from the common precursor (R)-N,N-dimethyl-1-[(S)-2-{3-(1-phenyl)-1H-pyrazolyl}ferrocenyl]ethylamine (7a). 7a was obtained in three steps and relatively low yield from the known 1-(R)-N,N-dimethylferrocenylethylamine (4). Nucleophilic substitution reactions of the dimethylamino group of 7a using secondary phosphines or pyrazoles led to P,N- and N,N-chelating ligands, respectively, that were used in Pd-catalyzed allylic substitution reactions, affording in part high enantioselectivities. X-ray crystallographic studies of 1-{(R)-1-[(S)-2-{3-(1-phenyl)-1H-pyrazolyl}ferrocenyl]ethyl}-3,5-dimethyl-1H-pyrazole (9a, C26H26FeN4, a = 8.417(7), b = 13.268(10), c = 20.222(10) Angstrom, orthorhombic, P2(1)2(1)2(1) (No. 19), Z = 4), the cyclic diferrocenyl derivative (R,S)-(S,S)-10 (C42H36Fe2N4, a = 10.312(3), b = 12.929(5), c = 24.391(8) Angstrom, orthorhombic, P2(1)2(1)2(1) (No. 19), Z = 4), and the complex [Pd(eta(3)-C3H5)((R)-(S)-9b)][P-6]. CH2Cl2 (12, C37H41F6FeN4PPd . CH2Cl2, a = 13.331(8), b = 38.49(2), c = 7.601(4) Angstrom, orthorhombic, P2(1)2(1)2(1) (No. 19), Z = 4), (R)-(S)-9b = 1-{(R)-1-[(S)-2-{3-(1-phenyl)-1H-pyrazolyl}ferrocenyl]ethyl}-3-(1-adamantyl)-1H-pyrazole) have been carried out.