Thiochromans and Thiochromones

Thiochromans and Thiochromones.—The spirothiochroman (175) has been synthesized from 3-methylene-l/7-2-benzothiopyran-4(3//)-one (176) and its stereochemistry has been examined, using X-ray crystallography. Modifications which have been made to Dianin s compound (see also under Chromans ) include replacement of the ring oxygen by sulphur. Some such compounds retain the clathrate-forming ability of the original molecule. 

Thiochroman (177) reacts with diethyl diazomalonate, with copper bronze as a catalyst, to form the sulphonium ylide (178) in high yield. Solvolysis of this in acetic acid gave 2-acetoxythiochroman (179) and thiochroman.  

---