ChemInform Abstract: Thieno(3,4‐f)‐2,1‐benzisothiazole. Synthesis and Physical Properties of a Novel Fused 14π Heteroarene as well as Its Thermal Cycloaddition Reactions with N,N‐Double Bond Systems.

Abstract

194 ChemInform Abstract The dione (I) reacts with P4S10 to give the (thermally stable) title compound (II) which contains three masked dipolar systems, represented by the limiting formulas α, β and γ. On cycloaddition reactions with diazadienophiles, (II) shows a decided locoselectivity": whereas involvement of the β-form is responsible for a (3 + 2) cycloaddition leading, on reaction with the triazolinedione (III), to compounds (IV), the azodicarboxylic esters (V) react with the 1,4-dipole γ to afford the adducts (VI). The former compounds undergo slow retro-scission even at room temp., whereas the latter are stable up to 130 rc C.