No abstract

A new prediction model for the autocatalytic random hydrolysis of aliphatic polyesters is proposed. The model predicts changes in the number-and weight-average degrees of polymerization. The model enables to avoid certain errors liable to occur in the estimation of hydrolysis with only the number-average molecular weight. The prediction model successfully interpreted the hydrolysis data of some aliphatic polyesters, such as poly(p-dioxanone), poly(β-propiolactone), poly(L-lactic acid), etc.

cu,P-Unsaturated thiocarbonyl S-sulfides (thiosulfines) 10 were generated by sulfurization of the thioketones 5 and were intramolecularly trapped as 1,5-dipoles giving 8, whereas, in the presence of Et3N, they were transformed by trans-sulfurization via 1,5 cyclization into the thioketones 13 capable of undergoing the intramolecular hetero-Diels-Alder reaction to give cycloadducts 9.

a,P-Unsaturated thioketones 4 , 5 and 9, which are formed in situ by thionation of the corresonding ketones, undergo intramolecular hetero Diels-Alder reactions with high regio-and diastereo-selectivities (transkis) to give dihydrothiopyran-fused cycloadducts 6, 7 and 10.Intramolecular Diels-Alder reactions provide useful methods cedures However, IHDA reactions involving a thiofor construction of polycyclic systems, and have been widely carbonyl function have received little attention so far, applied in organic synthesis.1 Intramolecular hetero Diels-examples being restricted to the internal trapping thio-Alder (IHDA) reactions are also powerful synthetic pro-aldehyde intermediates by dienes.3 We now report the first