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In explorations of synthesis and chemistry of spiroheterocycles, we found that reaction of aromatic nitrile oxydes with methylene γ‐butyrolactones (at room temperature) produced spiroheterocycles 4, 5 and 6. When cycloadditions were carried out in refluxing toluene, the methylene(5H)furan‐2‐one 3 gives a totally unexpected product 8.
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Fihi et al. (1995) studied this question.
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