Nucleophilic aromatic addition. Part IX: A route from 1,3,5‐trinitrobenzene to a dinitro‐tropane derivative

Abstract

Abstract1,3,5‐Trinitrobenzene takes up three methylene groups from diazomethane at −80° to give 1 (Scheme 1).Reduction of I with NaBH4 in pyridine yields the dihydro derivative II by saturation of the nitro‐olefinic double bond in I.In a protic solvent like methanol, this reaction proceeds with rupture of the isoxazoline‐N‐oxide ring, and leads to the intermediary formation of a nitroso‐and a primary alcohol‐function. The nitroso‐group reacts spontaneously further with a nearby HCNO2‐fragment, and this transannular process generates the tropane ring‐system of III. The hydroxyl‐group at the nitrogen‐bridge is easily oxidised, to give a relatively stable nitroxide, detectable by ESR. Spectral data, including X‐ray analysis of III1 fully confirm the proposed structures.