SYNTHESIS OF DUPEYREDIOXYL, A FERROMAGNETIC NITROXIDE BIRADICAL

Crystals of dupeyredioxyl 1 (1,3,5,7-tetramethyl-2,6-diazaadamantane-2,6-dioxyle), a nitroxide biradical, show ferromagnetic interaction at low temperature. This paper describes the synthesis of this molecule. Starting from 1,5,7-trimethyl norpseudopelletierine 2 a single amino acid has been obtained in 88% yield by hydantoin synthesis. Hofmann-Hoffler-Freytag reaction on the corresponding methyl ester gives the 3,5,7-trimethyl-2,6-diazaadamantane-1-carboxylic acid 6 in 76% yield. In order to transform the acid function into a methyl group, this acid was reduced to the 3,5,7-trimethyl-2,6-diazaadamantane-1-methanol 9 and then oxidized to the biradical 1-hydroxymethyl-3,5,7-trimethyl-2,6-diazaadamantane-2,6-dioxyl 10. Its hydroxymethyl function was converted into a methyl group by mesylation and reduction first to the bis-hydroxylamine mesylate 12 by treatment with 1,2-diphenylhydrazine and then to 2,6-dihydroxy-1,3,5,7-tetramethyl-2,6-diazaadamantane 13 by lithium aluminium hydride in tetrahydrofuran. The yield of the conversion of the hydroxymethyl group into a methyl group, from 10 to 13 is 68%. 13 is then oxidized to 1. The total yield from 1,3,5-trimethyl norpseudopelletierine 2 is 13%.