Easy Synthesis of New Chiral Tetradentate N₄ Schiff Bases and Their Use as Ligands for Metal Complexes

Abstract

The chiral N4 Schiff bases (1R,2R)‐N,N′‐bis(2‐p‐tosylaminobenzylidene)‐1,2‐diaminocyclohexane (H2CyTs, 1), (1R,2R)N,N′‐bis(2‐trifluoromethylsulfonaminobenzylidene)‐1,2‐diaminocyclohexane (H2CyTf, 2), (1R,2R)‐N,N′‐bis(2‐aminobenzylidene)‐1,2‐diaminocyclohexane (3) and (1R,2R)‐N,N′‐bis(2‐nitrobenzylidene)‐1,2‐diaminocyclohexane (4) were synthesized by a new and easy method in high purity and good yields. All the organic compounds were characterized by elemental analysis, mass spectrometry, IR and 1H and 13C NMR spectroscopy. Divalent Co, Cu and Ni complexes 5−8, containing the sulfonamide ligands 1 or 2, have been prepared and characterized. The X‐ray crystal structures of complexes [Co(1R,2R)‐CyTs] (6) and [Ni(1R,2R)‐CyTf] (8) have been solved. These complexes are potential precursors for homogeneous asymmetric catalysis of a variety of reactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Synthesis and Characterization of Homoleptic and Heteroleptic Cobalt, Nickel, Copper, Zinc and Cadmium Compounds with the 2‐(Tosylamino)‐N‐[2‐(tosylamino)benzylidene]aniline Ligand

“…In addition, both bonds are shorter than the range [2.030(6)-1.905(2) Å] described for tetracoordinate Ni II complexes with Schiff bases containing nitrogen amide donor atoms. [19][20][21][22][23] The Ni-O tosyl bond length of 2.004(4) Å is also shorter than those found in hexacoordinate complexes with ligands containing sulfon- …”

“…[19][20][21][22][23] The Ni-N amide bond lengths [1.833(5) and 1.895(4) Å] are significantly different to each other. In addition, both bonds are shorter than the range [2.030(6)-1.905(2) Å] described for tetracoordinate Ni II complexes with Schiff bases containing nitrogen amide donor atoms.…”

“…19(14) N ( (9) the amide nitrogen atoms and this seems to be the result of an attempt to minimize the steric hindrance between the tosyl groups. [19][20][21][22][23] The Ni-N amide bond lengths [1.951 (3) [19][20][21][22][23] The Ni-P bond length [2.3287(13) Å] does not differ significantly from the value observed in the tetracoordinate complex dibromo[N-2(diisopropylphosphanyl)benzyl]-N,N-dimethylaminonickel(II), [32] but is greater than those found in other tetracoordinate nickel(II) complexes in which phosphorus is a donor atom (2.168-2.199 Å). [33,34] As in the complexes [NiL] and [CuL], the Schiff-base ligand is again orientated in such a way that one of the oxygen atoms from a tosyl group is close to the nickel atom [distance Ni (1) complexes that contain donor oxygen tosyl ligands.…”

An efficient and high-yielding protocol for the production of Regorafenib via a new synthetic strategy

“…During the process for the reduction of 6, four typical methods utilizing hydrazine hydrate [14][15][16], iron powder [17,18], zinc dust [19][20][21] and palladium [22][23][24] were screened (Table 3). At the initial stage, reduction of 6 with hydrazine hydrate was incapable of thoroughly converting nitro to amino, along with the The optimization results were estimated by detecting the purity of the next-step product 7 and the two- An efficient and high-yielding protocol for the production… formation of impurities 7e and 7f (Fig.…”

Crystallographic report: [N,N′-Bis-(6-methylpyrid-2-ylium)-(1R,2R)-1,2-diaminocyclohexane] bis-[(p-cymene)- trichlororuthenate(II)]

“…calc. (d,6H, ). Diffraction data were collected on a Nonius Kappa-CCD diffractometer using Cu Kα radiation.…”