Organic heterocyclothiazenes. Part 17. Preparation, acylation, and metallation of 1,3,5,2,4-trithiadiazepine

Abstract

A larger scale preparation, with higher volume efficiency, is described for trithiadiazepine 3, which can be acylated with acid anhydrides in the presence of trifluoromethanesulphonic acid. 6-Acetyltrithiadiazepine 10 is brominated to 11, nitrated to 12, and oxidised to the corresponding glyoxal 16 and carboxylic acid; it forms an oxime and phenylhydrazone sluggishly. Trithiadiazepine is readily mercuriated to give the bis(acetoxymercuri) derivative 20 in high yield and the mono(acetoxymercuri) derivative 19 in low yield. 6-Bromotrithiadiazepine can also be mercuriated, under more vigorous conditions, but 6-nitrotrithiadiazepine is unexpectedly converted into bis(6-nitrotrithiadiazepinyl) mercury 22(with linear C–Hg–C bonds) which can be cleaved with iodine to give 6-iodo-7-nitrotrithiadiazepine. In contrast with mercuriation, thalliation of the trithiadiazepine 3 with thallium tris(trifluoroacetate) gives only the mono-metallated product 8, which is readily converted into the corresponding cyano, iodo, and methoxycarbonyl trithiadiazepines.