Reaction of 2,4-dinitrofluorobenzene with enediamines. synthesis of cinnolines
As we have shown previously, enediamines 1 can cyclocondense with aromatic electrophiles (aldehydes and esters) containing an active halogen atom in an ortho position to the electrophilic group to give condensed aminoazines [1-3]. The reaction occurs chemoselectively, the aromatic halogen atom being substituted by the carbon of the nucleophilic center of the enediamine and an amino group reacts with an exocyclic electrophilic group. In this work we have studied the use of nitro as the electrophilic group. Similar cyclizations involving nitro and amino groups are well known [4-6]. The reaction of the enediamines 1 with 2,4-dinitrofluorobenzene (2) occurs smoothly at room temperature to give a high yield of the products of substitution of the fluorine atom by the -carbon of the enediamine 3. Subsequent cyclization at the nitro group in the presence of sodium hydride under the conditions reported in [7] gives the cinnoline 1-oxides 4.