Asymmetric Carbon−Carbon Coupling of Phenols or Anilines with Aryllead Triacetates
journal contributionposted on 19.04.2002, 00:00 by Taichi Kano, Yuki Ohyabu, Susumu Saito, Hisashi Yamamoto
The asymmetric coupling of various phenol or aniline derivatives with bulky aryllead triacetates was thoroughly investigated using optically active amines, including strychnine and brucine. We found that conformationally restricted tertiary amines, as well as lithium aryloxides and molecular sieves, are essential for accelerating the rate of phenol coupling. Consequently, the reaction can be carried out at a low temperature (−40 to −20 °C) and gives a high degree of diastereo- and enantioselectivity. In contrast to the effectiveness of lithiation in phenol coupling, magnesation of anilines was a critical technique for aniline coupling with aryllead triacetates. Using these coupling methods, a diverse set of di-, tri, and polyaryl compounds with axial chirality can be easily obtained, and these should be useful for the construction of a variety of aryl−aryl frameworks involved in metal ligands, natural products, and artificial helical polymers.