Organic heterocyclothiazenes. Part 16. Reactions of trithiadiazepyne with cyclopentadienones. Some stable norbornadienones

Abstract

Trithiadiazepyne reacts with 2,5-dimethyl-11a and 2,5-diethyl-3,4-diphenylcyclopentadienone 11b in hot acetonitrile to give the initial Diels–Alder cycloadducts, 12a and 12b, which are remarkably stable norbornadienones. It reacts similarly with 2-methyl-3,4,5-triphenylcyclopentadienone 15 in cold acetonitrile to give the less stable carbonyl-bridged adduct 28. These initial cycloadducts readily lose carbon monoxide when heated to give the aromatic benzotrithiadiazepines, 13 and 29. In the reaction of trithiadiazepyne with phencyclone 8 the decarbonylated product 9 is the first to be isolated. With tetracyclone 2, and with the methyltriphenyl analogue 15 in hot acetonitrile, two molecules of the aryne are involved and more extensive reactions result in formation of the dithiins, 3 and 16, respectively. Stronger heating of the benzotrithiadiazepines induces a molecular arrangement with loss of nitrogen to give benzo-1,2,3-trithioles, 10, 14a,b and 17. A reaction sequence is proposed (Scheme 6) to explain the formation of all of these products.