Reactions of Bis(N,N'-bicyclic) Diazenium Dications

Article abstract of DOI:10.1021/jo00090a028

Eleven bis(N,N'-bicyclic) diazenium dications were generated from the corresponding hydrazines by NOPF6 oxidation.Their reactivity depends greatly upon the sizes of the bicyclic rings. (We designate bicyclic ring size using the number of atoms in the two bridges in addition to the dinitrogen bridge all the compound share.) Compounds with <*> rings alkylate acetonitrile at 240 K by opening a C_α-N(+) bond to produce a trialkyldiazenium cation, with ΔG(excit.) for the reaction increasing by at least 5.5 kcal/mol as the second bicyclic ring size increases.Compounds with an unsaturated bridge also alkylate acetonitrile; 22/u22(2+) only cleaves the <*> bridge and reacts faster than 21/22(2+), which only cleaves the <*> bridge.C_α-N(+) cleavage of <*> and larger rings by acetonitrile has not been observed. 21/22(2+) is significantly more acidic than 22/22(2+), but both are β-deprotonated by pyridine to produce aminoaziridinium cations at 240 K.At least mostly the exo <*> ring proton is lost from 21/22(2+).Dications with <*> and <*> bridges deprotonate at the α-carbon instead of the β-carbon, and 22/23(2+) is slightly more kinetically acidic than 21/22(2+). 22/24(2+) is deprotonated rapidly by ether at 235 K.