Non-terminal acetylenic esters react with many thiocarbonyl compounds to form heterocycles or 1: 1 addition products. Propiolic esters in most cases form isomeric mixtures of dimethyl 3, 3′-thiodiacrylates (I). The stereochemical course of the thiolic nucleophilic additions may be controlled for preparative purposes by changes in solvent polarity. All three stereoisomers of (I) have been prepared. The trans-isomer of methyl 3-(1, 1-dimethyl ...
![4-methyl-5-thia-1,7-diazabicyclo[4.3.0]nona-3,6-dien-2-one结构式](https://image.chemsrc.com/caspic/233/20620-10-4.png)