1087-64-5Relevant academic research and scientific papers
Ring-opening polymerization of l-lactide by organotin(IV)alkoxides, R2Sn(OPri)2: Estimation of the activation parameters
Chisholm, Malcolm H.,Gallucci, Judith C.,Krempner, Clemens
, p. 4436 - 4444 (2008/10/09)
The ring-opening polymerization of l-lactide, l-LA, to give poly-l-lactide by R2Sn(OPri)2 compounds, where R = Bun and p-XC6H4 (X = CF3, F, H, Me and OMe) has been studied in benzene over a temperature range. There is a relatively small variation in ΔH≠ as a function of R with all the values falling within the range 11 ± 2 kcal mol-1. The entropy of activation, ΔS≠, is consistently large and negative, -50 ± 5 eu, supporting the view that the ring-opening event, the enchainment step involves a highly ordered transition state. The crystal and molecular structures of the compounds Ph2Sn(OPri)2, (p-FC6H4)2Sn(OPri)2 and (p-Me2NC6H4)3SnOPri are also reported. While the latter compound is monomeric in the solid state the former are both dimeric with a pair of bridging OPri ligands.
A study of the ring-opening of lactides and related cyclic esters by Ph2SnX2 and Ph3SnX compounds (X = NMe 2, OR)
Chisholm, Malcolm H.,Delbridge, Ewan E.
, p. 1167 - 1176 (2007/10/03)
Ph3SnX reacts with L-lactide in the order X = NMe 2～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. Ph 3SnNMe2 reacts with cyclic esters and propylene carbonate at low temperatures to give isolable ring-opened products. The compound Ph 3Sn[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)NMe 2]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(OPr i)2 and L-lactide but is more labile toward further ring-opening of L-lactide.
