Bis-ortho-substitution by methyl groups dramatically increases the racemization barrier of Tröger bases.

We have shown through racemization kinetics studies that the enantiomerization barriers of the bis-ortho-methyl substituted Tröger bases 2 and 3 in acidic media are raised by 30 kJ mol(-1) relative to the parent compound 1, that is 130.4(4) and 131.6(4) kJ mol(-1), respectively (105 degrees C, pH 1, ethylene glycol).