Kinetic and equilibrium protonation of some alkylated 1,8-diaminonaphthalene monocations to form dications: carbon versus nitrogen protonation

Abstract

1-Dimethylamino-8-trimethylammoniumnaphthalene tetrafluoroborate (1) is protonated at equilibrium at N, C-2, and C-4 in the ratio 1 :15:4, but kinetically controlled protonation is exclusively at nitrogen. Deuteriation occurs more rapidly at C-4 than C-2, and probably involves rate-limiting ring inversion in the non-planar C-protonated ions. At equilibrium, diprotonation of NNN′N′-tetra-alkylated 1,8-diaminonaphthalenes (2)–(10) can occur predominately at N,N or N,p-C, depending on the alkyl groups. Kinetically controlled protonation of 1,8-bis(dimethylamino) naphthalene (2) and of 1,8-dipyrrolidinylnaphthalene (3) is exclusively on nitrogen.