Novel 9,9-diol systems starting from a 3,7-diazabicyclo[3.3.1]nonan-9-one nucleus-single crystal X-ray diffraction analysis of 3-(2-propyl)-7-benzyl-3,7-diazabicyclo[3.3.1]nonan-9,9-diol hydrobromide, 3-(2-propyl)-7-[3,4-dimethoxybenzyl)-3,7-diazabicyclo[3.3.1]nonan-9,9-diol hydrobromide, and 3,7-diisopropyl-3,7-diazabicyclo[3.3.1]nonan-9,9-diol dihydrochloride

Attempts to make inorganic metal complexes of 3,7-diazabicyclo[3.3.1]nonan-9-ones and metal bromides in fresh, reagent-grade, undried THF generated rare 9,9-diols. Treatment of the ketones with anhydrous HBr(g) in anhydrous ether gave hydrobromides with the proton on nitrogen and with the carbonyl group Intact. The hydrobromides were extremely hygroscopic and exhibited a strong propensity to form the corresponding 9,9-diol system. The mechanism of formation of the diols is discussed as well as a rationale for the stability of such diols via H-bonding in the solid state. The X-ray diffraction analyses of 3-(2-propyl)-7-benzyl-3,7-diazabicyclo[3.3.1]nonan-9,9-diol hydrobromide, 3-(2-propyl)-7-(3,4-dimethoxybenzyl)-3,7-diazabicyclo[3.3.1]nonan-9,9-diol hydrobromide, and 3,7-diisopropyl-3,7-diazabicyclo[3.3.1]nonan-9,9-diol dihydrochloride revealed a proton on N(3) and all bicyclic systems as chair-chair conformations in the solid state. The dihydrochloride was, of course, also protonated on N(7). This is the first systematic study of this type of 9,9-diol of the 3,7-diazabicyclo[3.3.1]nonane system and the corresponding carbonyl-containing hydrobromides with the proton on a nitrogen atom [N(3)].