Copper complexes bearing methylthiophenyl and methylfuranyl derivatives of (R,R)-1,2-diaminocyclohexane: X-ray structures and catalytic exploitation in Henry reaction

Two novel dichloro Cu(II) complexes of (R,R)-N1,N2-bis((5-methylthiophen-2-yl)methyl)cyclohexane-1,2-diamine (MTCHD) and (R,R)-N1,N2-bis((5-methylfuran-2-yl)methyl)cyclohexane-1,2-diamine (MFCHD) ligands have been synthesised and structurally characterised using X-ray diffraction. The geometry around the Cu(II) centres was distorted square planner. A strong Cu…Ofuranyl interaction exists in Cu(MFCHD)Cl2 that leads to the disappearance of original C2-symmetry of the ligand, resulting in selective R,S-coordination of N atoms in (1R,2R)-1,2-diaminocyclohexane. Catalytic activities of dichloro and diacetato Cu(II) complexes with 3 mol% of iPr2NEt were assessed in asymmetric Henry reactions that resulted in moderate to high yields with an enantiomeric excess up to 92%, without air/moisture exclusion.

Graphical abstractNovel Cu complexes ligated to methylthiophenyl and methylfuranyl derivatives of (R,R)-1,2-diaminocyclohexane were synthesized and characterized by X-ray diffraction. The original C2-symmetry was lost upon complexation to Cu(II) centre and resulted in selective R,S-coordination of N atoms in case of furanyl containing ligand. The dichloro and diacetato derivatives proved to be active catalysts in asymmetric Henry reaction with moderate yields and enantioselectivities up to 92%.Figure optionsDownload full-size imageDownload as PowerPoint slide