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17.2.2.1.3.4 Method 4: Reactions of 1,2,4,5-Tetrazines with Imidates or Thioimidates

DOI: 10.1055/sos-SD-017-00553

Lindsley, C. W.; Layton, M. E.Science of Synthesis, (200417387.

1,2,4,5-Tetrazines are highly reactive dienes in inverse electron demand DielsAlder reactions and react not only with alkynes and alkenes, but also with imidates, nitriles, and related compounds. For example, the reaction of dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate (144) with the imidates 145 (X=O) affords the adducts 146.[‌44‌] These undergo chelotropic expulsion of nitrogen to provide 1,4-dihydro-1,2,4-triazines, which rapidly eliminate ethanol to form the diesters 147 (Scheme 57). Unfortunately, yields are quite low (1333%), but when thioimidates 145 (X=S) are used as the dienophiles superior yields (6472%) are seen.[‌45‌,‌46‌]

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