Azaazulene als Dienophile in der Diels‐Alder‐Cycloaddition mit 3,6‐Bis(trifluormethyl)1‐1,2,4,5‐tetrazin
- 1 February 1993
- journal article
- research article
- Published by Wiley in European Journal of Inorganic Chemistry
- Vol. 126 (2) , 441-445
- https://doi.org/10.1002/cber.19931260222
Abstract
Azaazulenes as Dienophiles in the Diels‐Alder Cycloaddition with 3,6‐Bis(trifluoromethyl)1‐1,2,4,5‐tetrazineThe LUMO‐diene‐controlled [4 + 2] cycloaddition of the azaazulenes 6 and 17 with the tetrazine 1, one of the most reactive diazadienes “with inverse electron demand”, are described. Like azulene (2) the azaazulenes 6a, b react with 1 – probably by a two‐step mechanism via the dipolar species 7 – to yield the adduct 8; N2 elimination leads to 9, which rearranges to the pyridazo[4,5‐c]quinoline 13 and the azine‐substituted 1‐azaazulene 12. In a rather complex reaction sequence the 2‐azaazulene 17 forms the salt 18; the crystal structure of 18 has been determined by X‐ray diffraction methods.Keywords
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