AbstractIt is shown that azulene (1) and dimethyl acetylenedicarboxylate (ADM) in a fourfold molar excess react at 200° in decalin to yield, beside the known heptalene‐ (5) and azulene‐1,2‐dicarboxylates (6), in an amount of 1.6% tetramethyl (1RS,2RS,5SR,8RS)‐tetracyclo[6.2.2.22,501,5]tetradeca‐3,6,9,11,13‐pentaene‐3,4,9,10‐tetracarboxylate(‘anti’‐7) as a result of a SHOMO (azulene)/LUMO(ADM)‐controlled addition of ADM to the seven‐membered ring of1followed by aDiels‐Alderreaction of the so formed tricyclic intermediate16(cf. Scheme 3) with a second molecule of ADM. The structure of ‘anti’‐7 was confirmed by an X‐ray diffraction analysis. Similarly, the thermal reaction of 5,7‐dimehtylazulene (3) with excess ADM in decalin at 120° led to the formation ofca. 1% of ‘anti’‐12, the 7,12‐dimethyl derivative of‘anti’‐7, beside of the corresponding heptalene‐10and azulene‐1,2‐dicaboxylated (cf Scheme 2). The introduction of Me groups at C(1)and C(3)of azulene (1) and its 5,7‐dimethyl derivative3strongly enhance the thermal formation of the corresponding tetracyclic compound. Thus, 1,3‐dimethylazulene (2) in the presence of a sevenfold molar excess of ADM at 200° yielded 20% of ‘anti’‐9beside an equal amount of dimethyl 3‐mehtylazulene‐1,2‐dicarboxylate (8;cf. Scheme 1), and 1,3,5,7‐tetramethylazulene (4) with a fourfold molar excess of ADM AT 200° gave a yield of 37% of‘anti’‐15beside small