CHAPTER 3: Question 6

 

Simple Answers

The molecules are chiral since there is a stereoaxis along the bond between the phenyl ring bearing the R substituent and the nitrogen atom to which it is attached. The rate at which the two atropisomers interconvert decreases as the size of R increases since the planar (achiral) transition state increases in energy as the size of the R group increases. If R = H, then the compound is no longer chiral.

This example is taken from: A. Ohno, J. Kunitomo, and Y. Kawai; Tetrahedron, 1997, 53, 4601-10.

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