A novel reactivity pattern of nitro-benzofuroxans and -benzofurazans: the heterodienic behaviour of the five-membered ring.
Evidence is presented that the N3C9C8N fragment of the annelated ring of some nitro-activated benzofuroxans and benzofurazans acts as a heterodiene contributor upon treatment with cyclohexadiene, thus highlighting a new facet of the reactivity of this class of heterocycles.