A study of the ring-opening of lactides and related cyclic esters by Ph<sub>2</sub>SnX<sub>2</sub>and Ph<sub>3</sub>SnX compounds (X = NMe<sub>2</sub>, OR)
作者:Malcolm H. Chisholm、Ewan E. Delbridge
DOI:10.1039/b300101f
日期:——
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)
pH值3 SNX发生反应与大号的顺序X -丙交酯= NME 2〜OME » OPR我> OBU吨在初始开环事件。开环率甲基 取代的1,4-二恶烷-2,5-二酮随着 甲基没有观察到3,3,6,6-四甲基-1,4-二恶烷-2,5-二酮的取代和开环。通过对Ph 3 SnOPr i与L-丙交酯之间反应的研究,确定了活化参数ΔH ≠ = 13(1)kcal mol -1和ΔS ≠ = -37(3)eu。Ph 3 SnNMe 2与环状反应酯类和碳酸亚丙酯在低温下得到可分离的开环产物。化合物Ph 3 Sn [OCHMeC(O)OCHMeC(O)X](其中X = NMe 2,OMe)在室温下不稳定,产生Ph 3 Sn [OCHMeC(O)X]和Ph 3 Sn [OCHMeC (O)] ñ X,其中ñ ≥ 3,通过酯交换反应,与其它次要产物由于沿苯基/ OR组转移(即Ph 4 Sn)。Ph 2 Sn(NMe