Synthesis and properties of stable 1,2,3,4,5,6,7-heptamethoxycarbonylcyclohepta-2,4,6-trien-1-yl potassium and its reactions with electrophilic reagents

A new original one-pot procedure for the synthesis of a heptaester substituted cycloheptatriene from simple starting compounds, alkyl diazoacetate and 2,3-dibromosuccinate in pyridine was discovered. This compound, upon action of base, easily gives rise to the corresponding cycloheptatrienyl anion, which can be isolated as a stable salt. NMR and X-ray data of the compounds obtained are given. Reactions of this anion with electrophiles (methyl iodide, allyl bromide and diazonium salts) were also studied. In the last case, the 3a,7a-dihydroindazole derivatives were obtained as isolated products.