J. Velzen, C. Kruk, K. Spaargaren
Sep 2, 2010
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Recueil des Travaux Chimiques des Pays-Bas
Abstract
1,3,5-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.