Achieving conformational control over C-C, C-N and C-O bonds in biaryls, N,N'-diarylureas and diaryl ethers: advantages of a relay axis.

The orientation of Ar-C, Ar-N and Ar-O bonds in biaryls, N,N'-diarylureas and diaryl ethers (whose conformers are distinguishable by NMR) may be controlled with a selectivity up to >95 : 5 by an adjacent stereogenic centre; the selectivity may be greater when a second stereogenic axis is inserted between the controlling centre and the slowly rotating bond.