Studies of aminotriazinones: cycloproparenone precursors?

Abstract

The photolysis of 3-lithio ((p-tolysulfonyl)amino) -1,2,3-benzotriazin-4-(3H)-one 1 in methanol gave among other products, 2-TsNHNHC$\sb6$H$\sb4$CO$\sb2$Me and not the reported 2-MeOC$\sb6$H$\sb4$CONHNHTs, suggesting the intermediacy of an azetidinone/iminoketene 2 rather than a 1,4-dipole 3 in these systems. The photolysis of 1 in THF gave, in addition to products derived solely from the tosyl group, 3-tosyloxyindazole 4 rather than the expected 1-tosylindazolin-3-one 5 or 2-tosylindazolin-3-one 6, arising from 3 and 2 respectively. Evidence is presented that 5 and/or 6 are initially formed from 1 and then rearrange to 4 by photodetosylation/tosylation via indazolin-3-one, or possibly via a photo-Fries-like reaction. The formation of indazolinones from this reaction has implications regarding the intermediacy of benzocyclopropenone 7 during the photo-decomposition of 1. The oxidation of 3-aminothienotriazinones 8 gives a thiophene analog of 7 that exhibits the reactivity of an electron rich 1,3-bidentate pi system, reacting with electron-deficient carbonyl compounds, but not with electron-rich traps, to give lactones. During the preparation of 8 the reaction of methyl or ethyl 2-amino-4,5,6,7-tetrahydrobenzo (b) thiophene-3-carboxylate with hydrazine gave the corresponding pyrazolo (3.4-c) pyridazine via the expected 2-amino-4,5,6,7-tetrahydrobenzo (b) thiophene-3-carboxhydrazide.