Kinetic measurements to determine effective molarities of intramolecular re
actions using 2,4-pentanediol and related tethers showed that methyl groups
on the tether accelerate the major diastereomeric process but decelerate t
he minor process. The efficient promotion of stereocontrol is suggested to
be due to chiral perturbation of the reaction rate through the entropy term
, The conformation of the encounter complex of the reagent and reactant moi
eties was deduced by stereochemical analysis of the intramolecular adducts.