A new and simple procedure for the synthesis of heptamethyl cyclohepta-1,3,5-triene-1,2,3,4,5,6,7-heptacarboxylate in a 51% yield is presented. An optimization of the reaction conditions was performed, and a convenient protocol for the isolation of the reaction product was developed. The structure of the key electrophilic intermediate was determined by means of NMR spectroscopy, and a plausible reaction mechanism is proposed.

Two schemes for synthesizing heptasubstituted cycloheptatrienes with various substituents in the ring are suggested. The first method is based on cycloaddition of 2,5‐dimethoxycarbonyl‐3,4‐diphenylcyclopentadienone with substituted cyclopropenes and allows cycloheptatrienes containing two or three electron‐withdrawing substituents in the molecule to be obtained. The second method employs a cascade reaction between a substituted cyclopentadienone and appropriate vinyldiazoacetates. It allows the number of electron‐withdrawing substituents to be increased to five. In all cases, heptasubstituted cycloheptatrienes are formed as just one of the possible isomers.

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The mechanism for the reaction of dimethyl malonate with dimethyl acetylenedicarboxylate in the presence of pyridine and acetic acid to form isomeric octa(methoxycarbonyl)cycloheptadienes was established. The formation of intermediary N‐[di(methoxycarbonyl)vinyl]pyridinium acetate was proven by means of NMR spectroscopy. On the basis of the established mechanism, dimethyl dibromosuccinate was proposed to be used instead of dimethyl acetylenedicarboxylate. A novel method for the synthesis of penta(methoxycarbonyl)cyclopentadienylsodium through the reduction of hepta(methoxycarbonyl)cycloheptatriene with sodium borohydride, electrocyclic ring contraction and retro‐[2+2]‐cycloaddition was developed.

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