1,8-Diazabicyclo[6.6.6]eicosane,1,8-Diazabicyclo[6.6.5]nonadecane and 1,8-Diazabicyclo[6.6.4]octadecane and Their Diprotonated Forms

摘要

The preparation of the title compounds 9-11 was achieved by catalytic hydrogenation of l,8-diazabicyclo[6.6.6]eicosa-4,11-diyne (13),l,8-diazabicyclo[6.6.5]nonadeca-4,ll-diyne (14),and l,8-diazabicyclo[6.6.4]octadeca-4,ll-diyne (15),respectively.As catalyst we used Pd(OH)2 on carbon.NMR studies on 9-11 revealed an in/in conformation at the bridgehead positions.Treatment of 9-11 with an excess of trifluoroacetic acid yielded,in a kinetically controlled reaction,mixtures of the out/out and in/out diprotonated species [9(centre dot)2H]~(2+),[10(centre dot)2H]~(2+)and [11(centre dot)2H]~(2+).The thermodynamically controlled species,the corresponding in/in conformers,are formed at higher temperatures and longer reaction times.The experimental observations are supported by AMI calculations.