Variously substituted 1-phenyl-3,4-dihydroisoquinolinium compounds were prepared, in order to study their reactions with hydroxide ions concerning ring-chain isomerism of their products. Thereby was observed a dependence on the electrophilic properties of C-1 for forming the pseudo-bases and a ring opening tendency to the amino ketones by electron-withdrawing substituents at the nitrogen atom. Moreover steric effects caused by voluminous substituents in 1- and 2-positions also importantly affected the isomeric distribution. So the N-ethyl derivatives showed an enhanced dissociation of the hemiaminal to the quaternary iminium base. From a solution of the dihydroisoquinolinium salt 35 in [D6]DMSO after addition of NaOD until pH 10 resulted an equilibrium of the quaternary iminium base 36q, the pseudo-base 36a and the amino ketone 36b. These species were detected and assigned by NMR measurements.
Dimethyl Sulfoxide Electrochemistry