The chemistry of bicyclic bisureas. 3. The synthesis and hydrolytic stability of the difluoroborate salts of 3,7-diethoxy-2,6-diaza-4,8-diazoniabicyclo[3.3.0]octane-3,7-dienes and 3,7-diethoxy-2,6-diaza-4,8-diazoniabicyclo[3.3.1]non-ane-3,7-dienes

1. Unsubstituted and tetra-N-methyl-substituted bicyclic bisureas (BBU) of the octane and nonane series on reaction with triethyloxonium fluoroborate form O-alkylation products at both carbonyl groups, namely the difluoroborates of 3,7-diethoxy-2,6-diaza-4,8-diazoniabicyclo[3.3.0]octane-3,7-dienes and 3,7-diethoxy-2,6-diaza-4,8-diazoniabicyclo[3.3.1]nonane-3,7-dienes. 2. On hydroylsis of the O-alkylation products of tetra-N-methyl-substituted BBU, the reaction resulting in the fission of one of the rings predominates.