Asymmetric induction—V : Effect of R on asymmetric induction in additions to abcC-COR compounds

The diastereomeric product ratios from reactions involving the addition of various reagents to the carbonyl of φCH₃HC-COR compounds varies over a wide range. This variation is interpreted as due partly to changes in the structure of the diastereomeric transition states with changes in the size of R. For example, when R is smaller than the φCH₃HC group the diastereomeric product ratios are close to those predicted on the assumption that 1 and 2 are the minimum energy diastereomeric transition states; and when R is larger than the φCH₃HC group, the diastereomeric product ratios are large and closer to those that one might expect if 5 and 6 were the minimum energy transition states.