Chemistry of 1,3-dichloro-1,3-bis(dimethylamino)propenium cations: (1) attempted synthesis of cationic cyclophanes and (2) a computational study of an azapentalenium cation

The chemistry of 1,3-dichloro-1,3-bis(dimethylamino)propenium cation was explored for its potential as a linking fragment in the synthesis of cationic cyclophanes. Previous reports show E-H bond insertion to be a viable form of functionalization in propenium cations (E = O, N, P). Formation of cationic cyclophanes was attempted through addition of various bifunctional phenols to the transient chloropropargyl cation, generated in situ through deprotonation of the 1,3-dichloro1,3-bis(dimethylamino)propenium backbone. These reactions produced mixtures of various colours, indicative of reactivity. Unfortunately, the attempted synthesis of cationic cyclophanes produced a mixture of products, none of which were isolated. 1,3-Bis(dimethylamino)-4-azapentalene was identified as a minor byproduct during syntheses of cationic cyclophanes. The structural and electronic characteristics of 1,3-bis(dimethylamino)-4-azapentalenium cation was explored through ultraviolet-visible spectroscopy and mass spectrometry. Computational analysis of the 1,3-is(dimethylamino)-4-azapentalenium cation was done through nucleus independent chemical shift scans (NICS). The NICS scans show different tropicities in each ring, a trend not observed previously in bicyclic systems.