Tetrahedron

Dienophilicity of imidazole in inverse electron demand Diels–Alder reactions: cycloadditions with 1, 2, 4, 5-tetrazines and the structure of zarzissine

ZK Wan, GHC Woo, JK Snyder

Index: Wan, Zhao-Kui; Woo, Grace H.C.; Snyder, John K. Tetrahedron, 2001 , vol. 57, # 26 p. 5497 - 5507

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Citation Number: 43

Abstract

The inverse electron demand cycloadditions of 2-substituted imidazoles with dimethyl 1, 2, 4, 5-tetrazine-3, 6-dicarboxylate produced imidazo [4, 5-d] pyridazines in good yields. This chemistry was applied to the synthesis of 2-amino-1H-imidazo [4, 5-d] pyridazine (1), the structure reported for zarzissine, a cytotoxic marine alkaloid. Differences in the 1H-and 13C NMR spectra of 1 with those reported for zarzissine necessitated a structural revision, and ...