The bromination of 2,1,3‐benzothiadiazoles in 47% hydrobromic acid at elevated temperature has led to a general preparative method for the synthesis in high yield of otherwise difficulty accessible brominated 2,1,3‐benzothiadiazoles. The typical addition reaction is apparently eliminated under these reaction conditions and substitution takes place exclusively. Bromination of 2,1,3‐benzothiadiazole occurs successively at positions 4 and 7. 4‐Substituted 2,1,3‐benzothia‐diazoles are selectively brominated at position 7. 5‐Bromo‐ and 5‐methyl‐2,1,3‐benzothiadiazole are brominated consecutively at positions 4 and 7.

2,1,3‐Benzothiadiazolecarbonitriles, 2, have been prepared by two different methods. Reaction of bromo‐2,1,3‐benzothiadiazoles, 1, with cuprous cyanide occurs advantageously in refluxing dimethylformamide to give 2, complexed with curpous bromide. Hydrogen peroxide in hydrochloric acid at 30–40° is shown to be an effective reagent for efficient decomposition of these reactions complexes, 2 CuBr, and subsequent isolation of 2. Yields in the Sandmeyer method for preparing nitriles 2 were improved by diazotizing amino‐2,1,3‐benzothiadiazoles, 3, with nitrosyl‐sulfuric acid prior to reaction with the cuprous‐sodium cyanide complex.

Synthesis80 of Ethyl 3-(2-Indanyl)carbazate (33).-Addition of 0.5 ml of glacial acetic to a solution of 5.0 g (38 mmol) of 2-indanone81 and 4.3 g (41 mmol) of ethyl carbazate (purum Fluka) in 75 ml of ethanol (95%) at 50°g ave the precipitation of 6.0 g (28 mmol) of 2-indanone-N-carbethoxyhydrazone (34) in 5 min:

The redox behavior has been determined in acetonitrile solutions at a mercury and platinum electrode for 2,1,3‐benzo(group VI)diazoles, and 3,4‐disubstituted and fused 1,2,5‐thiadiazoles. The derivatives studied contained alkyl, phenyl, bromo, chloro, cyano, nitro, methylsulfonyl, and trifluoromethylsulfonyl groups. All ring systems and their derivatives are reversibly reduced initially in a one‐electron step, to their respective radical anion, but the nitro and bromo derivatives are reduced preferentially at the substituent group. The potential at which the production of the radical anion occurred became more anodic as the electron withdrawing ability of the substituent and the number of substituents increased.

amount of water present) during the titration. Therefore, all titrations were carried out at 0.005 M concentrations. The pKa point was always in the desired flat portion of the titration curve. The e.m.f. at half neutralization was taken as one-half the calculated stoichiometric end point. As mentioned above, the latter was always very close to the observed inflection point, and resulted in a maximum error of e.m.f. values of about 5 mv. Runs were carried out in duplicate. Repeat determinations were always within 10 mv. and generally within 5 mv.The collected Ae.m.f. values at half neutralization ( values, referred to N,N'-diphenylguanidine) are given in Table III. A plot of these values vs. literature pKj(H:0) values for several of these bases (diphenylguanidine, triethylamine, pyridine, acetamide, and urea) indicated a straight-line relationship, and so the p/Guno) values for the series of N,N-disubstituted amides are interpolated from this line (Tables I and III).The least-squares calculation of pifa(H¡o) vs. was pATa(HiO) = 10.10 -0.0118 , with a standard deviation of 33 mv.