反应详情

Thiophene (a) is reacted with succinic anhydride (c) under Friedel-Crafts reaction conditions to afford 4-(2-thienyl)-4-oxobutyric acid (XII). Substitution of benzene (b) in the above reaction affords 4-phenyl-4-oxobutyric acid (XVII). ##STR18## The oxobutyric acids of formulas (XII) and (XVII) obtained in Step 1 above, are reacted with a suitable 1,2-dithiol (d), R3 and R4 are each either hydrogen or methyl, in an aromatic solvent such as benzene, toluene or xylene, in the presence of catalytic amounts of p-toluenesulfonic acid at a temperature range of 25° to 120° C and, preferably, from 75° to 110° C while azeotroping the water formed in the reaction. Alternatively, the reaction is conducted in a C2 -C5 alkanoic acid, preferably, acetic acid in the presence of an acid catalyst such as boron trifluoride/methanol, boron trifluoride/ether, ZnCl2 /Na2SO4, HCl/ether, and the like, at the temperature range specified above, to afford 2-(2-thienyl)-1,3-dithiolanepropionic acid (XIII) and 2-phenyl-1,3-dithiolane-2-propionic acid (XVIII), respectively. R3 and R4 are as hereinabove defined. ##STR19## The dithiolane propionic acids of formulae (IIIa) and (IIIb) are converted to the corresponding acid chlorides of formulae (XIV) and (XIX) with oxalyl chloride or thionyl chloride (with a small amount of DMF added if desired) in an inert anhydrous solvent selected from the group consisting of benzene, toluene, xylene, chlorobenzene, at a temperature range of about 0° to 30° C and preferably 15° to 30° C. ##STR20##