Atropisomerism of the C-1-C′-1 axis of 2,2′,8,8′-unsubstituted 1,1′-binaphthyl derivatives

The Suzuki coupling of optically active (S)-binaphthyl bromide 10 with (S)-binaphthyl boronic acid 11 produced a diastereomeric mixture of tetrahydroxyquaternaphthyls 4. The coupling products 4 as well as their derivatives 5-7 can be considered as members of the family of 1,1 ' -binaphthyl-3,3 ' -diols. The C-1-C ' -1 axis of all these compounds was found to have an unusually high rotational barrier. Generally, the barrier is higher for derivatives having more bulky substituents at the 3 and 3 ' positions.