sequence to give 3,4-diazanorcaradienes 9 with endo configuration of the methyl group at C-7. On gentle heating in inert solvents, these 3,4-diazanorcaradienes 9 are cleanly transformed into semibullvalenes 11. This reaction sequence can also be performed as a one-pot method. Kinetic investigations and comparisons with two model systems are in agreement with the proposed reaction mechanism.
Two series of new s-tetrazine derivatives containing 1,3,4-oxadiazole and 1,3,4-thiadiazole rings were synthesized from s-tetrazine-3,6-dicarbohydrazide, triethyl orthoesters and aroyl chlorides. Cyclocondensation reactions for both groups of conjugated arrangements proceeded rapidly and efficiently under microwave irradiation. The obtained compounds exhibited luminescence properties and large quantum yield of emitted photons.
[4+2] Cycloadditions of 1,2,4,5-Tetrazines and Cyclopropenes − Synthesis of 3,4-Diazanorcaradienes and Tetracyclic Aliphatic Azo Compounds
1,2,4,5-Tetrazines 1 readily react with cyclopropenes 2 to form 3,4-diazanorcaradienes 3, 4, 7 and 8 in a cycloaddition − cycloelimination sequence. Compounds 3 and 4 still act as 1,3-dienes with cyclopropenes 2, producing aliphatic azocompounds 5 and 6, versatile starting compounds in thermolysis and photolysis reactions.