4,5-Dimethyl-thieno[3,2-d]isothiazolo-3(2H)-one-1,1-dioxides, compositions, and methods of use as a sweetener

#This invention relates to novel condensed isothiazolo-3(2H)-one-1, 1-dioxides and salts thereof, a method of preparing these compounds, and methods of using them as sweetening agents.

#More particularly, the present invention relates to a novel class of compounds represented by the formula ##STR2## wherein X is oxygen or sulfur;

#R.sub.1 is hydrogen, methyl or ethyl; and

#A mixture consisting of 20.5 gm (0.1 mol) of 5-methyl-2-sulfamoyl-furan-3-carboxylic acid, 20.8 gm (0.1 mol) of phosphorus pentachloride and 50 ml of anhydrous toluene was refluxed for eight hours. Thereafter, the hot reaction mixture was filtered, and upon cooling of the filtrate 11.8 gm (62.5% of theory) of 5-methyl-furo[3,2-d]isothiazole-3(2H)-one-1,1-dioxide of the formula ##STR5## crystallized out. The product was recrystallized twice from benzene, yielding 6.9 gm (37% of theory) of the purified product having a melting point of 195.degree.-196.degree. C. (decomp.).

#Analysis:

#IR (KBr): 1730 and 1690 cm.sup.-1 (CO);