Highly Stereoselective Synthesis of Novel Multistereogenic Bis-Bifunctional Ligands Based on [2.2]Paracyclophane- 4,7-quinone, their Structure Elucidation and Application in Asymmetric Catalysis

Abstract

Bis-bifunctional cis-4,7-diarylsubstituted-4,7-dihydroxy-4,7-dihydro[2.2]paracyclophanes 3-6 were synthesized by a highly diastereoselective reaction of ortho-substituted aryllithium reagents with [2.2]paracyclophane-4,7-quinone (1). Enantiomerically pure diols 3-5 were tested as chiral inductors in the enantioselective addition of diethylzinc to benzaldehyde (up to 93.5% ee). Acid dehydration of cis-4,7-di(2-methoxyphenyl)-4,7-dihydroxy-4,7-dihydro[2.2]-paracyclophane (3) results in 4,7-dihydro-7,8-di(2-methoxyphenyl)[2.2]paracyclophane-4-one (8) - a planar chiral cyclohexadienone of the [2.2]paracyclophane series with a para-semiquinoid substructure. X-Ray investigations of compounds 3, 4 and 8 were performed.