Zum mechanismus der semibullvalen-bildung aus 1,2,4,5-tetrazinen und bifunktionellen cyclopropenen

[4+2] Cycloadditions of 1,2,4,5-Tetrazines and Cyclopropenes − Synthesis of 3,4-Diazanorcaradienes and Tetracyclic Aliphatic Azo Compounds

“…[1] In the meantime this heterocyclic system has proved to be a valuable electron-poor diene in [4ϩ2] cycloadditions with anglestrained and electron-rich dienophiles. [8,9] Here we give a full report on the synthesis of 3,4-diazanorcaradienes 3, 4, 7 and 8, as well as for the aliphatic azo compounds 5 and 6. [8,9] Here we give a full report on the synthesis of 3,4-diazanorcaradienes 3, 4, 7 and 8, as well as for the aliphatic azo compounds 5 and 6.…”

Synthesis of strained ring systems for bioorthogonal labeling applications

“…containing unsymmetric tetrazines react up to three orders of magnitude faster than their symmetric analogs 35 . This means that by the choice of the right reagents the second order rate constant can change up 9 orders of magnitude 36 .…”

“…Our synthesis of 37 (Scheme 18.) started from (Z)-9-oxabicyclo[6.1.0]non-4-ene (35) by converting it to 36 in reaction with triethylene glycol monomethyl ether (3PEGMe) in the presence of erbium triflate 66 . To our delight, 36 could be distilled from the product mixture following an aqueous work-up and while it still contained some 10% of 3PEGMe, luckily was free of double bond containing impurities.…”