Novel conversion of a 3-oxidopyridinium into a 4-oxidoisoquinolinium
Abstract
Diels-Alder annelation of a 3-oxidopyridinium dimer followed by oxidation leads in high yield to a mixed 3-oxidopyridinium–4-oxidoisoquinolinium dimer which undergoes reversible dissociation to form a regioisomeric product; the 4-oxidoisoquinolinium is trapped as several adducts with dipolarophiles.