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Diels ‐ Alder Reactions of [2.2] Paracyclophan‐1‐ene and [2.2] Paracyclophane‐1,9‐diene with 3,6‐Disubstituted 1,2,4,5‐Tetrazines
Author(s) -
de Meijere Armin,
König Burkhard
Publication year - 1992
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19920750324
Subject(s) - tetrazine , chemistry , adduct , diene , ene reaction , medicinal chemistry , diels–alder reaction , crystal structure , dehydrogenation , stereochemistry , crystallography , organic chemistry , catalysis , natural rubber
[2.2] Paracyclophan‐1‐ene ( 1 ) and [2.2] paracyclophane‐1,9‐diene ( 6 ) apparently act as dienophiles with inverse electron demand and smoothly react with dimethyl 1,2,4,5‐tetrazine‐3,6‐dicarboxylate ( 2a ) at room temperature forming dihydropyridazine adducts, which are dehydrogenated to the pyridazino‐anellated [2.2] paracyclophanes 5a and 8a , respectively. The molecular structure of 5a is determined by X‐ray crystal‐structure analysis. Under more rigorous conditions, phenyl‐substituted derivatives 5b and 8b are obtained from 1 and 6 , respectively, with 3,6‐diphenyl‐1,2,4,5‐tetrazine. Compounds 1 and 6 are less reactive dienophiles than other strained cyclic olefins as shown by kinetic measurements.