Ph3SnX reacts with L-lactide in the order X= NMe2∼ OMe≫ OPri> OBut in the initial ring- opening event. The rate of ring-opening of methyl substituted 1, 4-dioxane-2, 5-diones decreases with methyl substitution and ring-opening of 3, 3, 6, 6-tetramethyl-1, 4-dioxane-2, 5-dione is not observed. From studies of the reaction between Ph3SnOPri and L-lactide the activation parameters ΔH≠= 13 (1) kcal mol− 1 and ΔS≠=− 37 (3) eu have been ...