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A new series of symmetrical 5,5'-disubstituted bl(2-thenoyl) peroxides was prepared, with the substituents chloro, bromo, methyl, t-butyl, and nitro groups. The unsymmetrical bmethylbis( Zthenoyl) peroxide and two new 4,4'-disubstituted bis-(2-thenoyl) peroxides, the 4,4'-dimethyl and 4,4'-dibromo compounds were also prepared. The thermal decomposition products of bis(2thenoyl) peroxides in carbon tetrachloride are 2-thenoic acid (20 mole per cent), carbon dioxide (20 mole per cent), and a polymeric material (46 per cent by weight of initial peroxide). In the presence of the free radical scavenger 3,4dichlorostyrene, a polymer was isolated which contained 2.95% sulfur. The rates of spontaneous thermal decomposition of the thenoyl peroxides in carbon tetrachloride were determined by conducting their decompositions in the presence of the efficient free radical scavenger, 3,4dichlorostyrene. In all cases studied, with the exception of bis( 5-nitro-2-thenoyl) peroxide, the decomposition rates followed strict first-order kinetics. In the absence of a free radical scavenger the rate of decomposition of bis(2-thenoyl) peroxide is much greater. The rate constants (75') show that electron-donating substituents on the thiophene rings accelerate the rate of decomposition, while electron-withdrawing substituents have the opposite effect. The Hammett equation was found applicable to the spontaneous decomposition of the substituted bis (2-thenoy1)peroxides.

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The synthesis and gastric acid antisecretory properties of several N-substituted thieno[3,4-d]isothiazol-3-amine 1,1-dioxides and analogues are described. Two of the more potent compounds, N-[3-[3-(1-piperidinylmethyl)phenoxy]propyl]thieno[3,4-d] isothiazol-3-amine 1,1-dioxide (6a) and N-[4-[3-(1-piperidinylmethyl)phenoxy]propyl]thieno[3,4-d] isothiazol-3-amine 1,1-dioxide, showed greater potencies as H2-receptor antagonists (in vitro) than ranitidine. They also had potent gastric acid antisecretory activities in vivo, inhibiting basal acid secretion in the rat, histamine-stimulated acid secretion in the dog, and food-stimulated acid secretion in the dog. These were selected for further pharmacological evaluation.

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