is so much faster than is rotation of the carbon-nitrogen bond that the stereochemistry is preserved. In this way the (M,S) isomer yields the (S,S) dihydroindolone.

The most important class of atropisomers are biaryls such as diphenic acid, which is a derivative of biphenyl with a complete set of ortho substituents. Heteroaromatic analogues of the biphenyl compounds also exist,