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 determined. Ph3SnNMe2 reacts with cyclic esters and propylene carbonate at low temperatures to give isolable ring-opened products. The compound Ph3Sn[OCHMeC(O)OCHMeC(O)X] (where X = NMe2, OMe) are labile in solution at room temperature, yielding Ph3Sn[OCHMeC(O)X] and Ph3Sn[OCHMeC(O)]nX, where n ≥ 3, by transesterification, along with other minor products due to phenyl/OR group transfer (i.e., Ph4Sn). Ph2Sn(NMe2)2 and L-lactide react to give Ph2Sn[OCHMeC(O)NMe2]2 by ring-opening of L-lactide followed by rapid amidation. A related compound, Ph2Sn[OCHMeC(O)OPri]2, is also formed in the reaction between Ph2Sn(OPri)2 and L-lactide but is more labile toward further ring-opening of L-lactide.
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