, 5-(3, 4-diethoxypheny1)-and, 5-(3, 4, 5trimeth-oxypheny1)-a-mercaptoacrylic acids (IC and Id) with an excess of iodine in dioxane at 70" for several hours afforded 5, 6diethoxybenzothiophene-2-car-boxylic acid (IIc) and 5, 6, 7-trimethoxybenzothiophene-2- carboxylic acid (IM) in fair to moderate yields. Interestingly enough, when@-(4-ethoxy- phenyl)-a-mercaptoacrylic acid was subjected to ring-closure conditions only tars were ...
![2-sulfanylidene-5-[(3,4,5-trimethoxyphenyl)methylidene]thiazolidin-4-one Structure](https://image.chemsrc.com/caspic/108/49581-16-0.png)