Novel C2-symmetric chiral O,N,N,O-tetradentate 2,2-bipyridyldiolpropane ligands: synthesis and application in asymmetric diethylzinc addition to aldehydes

First synthesis of C2-symmetric chiral O,N,N,O-tetradentate 2,2-bipyridyldiolpropane ligands is described. The Mukaiyama–Michael reaction was applied as an important reaction for the synthesis of 2,2-bipyridylpropane 9. Among the ligands synthesized, ligand 11 exhibits excellent chiral induction (up to 97% ee) in diethylzinc addition to various aldehydes. The use of additional Lewis acid such as Ti(OiPr)4 in diethylzinc addition reaction is not required for the present catalytic system.

Figure optionsDownload as PowerPoint slide

2,2′-(Propane-2,2-diyl)bis(6,6-dimethyl-5,6,7,8-tetrahydro-5,7-methanoquinoline)C27H34N2Ee ⩾97%[α]D20.7=+79.3 (c 1.00, CHCl3)Source of chirality: (1R)-(+)-α-pineneAbsolute configuration: (5S,5′S,7S,7′S)

2,2′-(Propane-2,2-diyl)bis(6,6-dimethyl-8-(1-hydroxy-1-methylethyl)5,6,7,8-tetrahydro-5,7-methanoquinoline)C33H46N2O2Ee ⩾ 97%[α]D20.0=-1.0 (c 4.20, CHCl3)Source of chirality: (1R)-(+)-α-pineneAbsolute configuration: (5S,5′S,7S,7′S,8R,8′R)

2,2′-(Propane-2,2-diyl)bis(6,6-dimethyl-8-(1-hydroxy-1-phenylethyl)-5,6,7,8-tetrahydro-5,7-methanoquinoline)C53H54N2O2Ee ⩾ 97%[α]D22.1=-303.2 (c 1.00, CHCl3)Source of chirality: (1R)-(+)-α-pineneAbsolute configuration: (5S,5′S,7S,7′S,8R,8′R)