Synthesis and thermal transformations of pyrazolines obtained by 1,3-dipolar addition of diazocyclopropane to maleimides |
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Authors: | I V Kostyuchenko E V Shulishov R R Rafikov Yu V Tomilov |
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Institution: | (1) N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russian Federation |
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Abstract: | 1-Pyrazolines, obtained by 1,3-dipolar cycloaddition of diazocyclopropane to N-phenyl- and N-cyclohexylmaleimides, undergo complete dediazoniation at 175 °C for 10–16 h with the formation of spiro3-azabicyclo3.1.0]hexane-6,1′-cyclopropane]-2,4-diones
3 (80–89%) and isomeric 3-cyclopropyl-1H-pyrrole-2,5-diones 4. On the example of 3-cyclopropyl-1-phenyl-1H-pyrrole-2,5-dione, it was shown that compounds 4 are able again to enter into 1,3-dipolar cycloaddition with diazomethane or diazocyclopropane with the reaction in the case
of diazocyclopropane being nonselective and leading to two regioisomeric pyrazolines in the ratio ∼1.7: 1, thermolysis of
which, conversely, proceeds with high selectivity and exclusively affords a spiropentane derivative. An action of the aqueous
methanol solution of sodium hydroxide on the spiropentanes fused with succinimide fragment and subsequent acidification of
the salts obtained lead to stable cis-amidoacids of spiropentane series.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1680–1685, August, 2008. |
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Keywords: | spiro[1-pyrazoline-3 1′ -cyclopropanes] spiropentanosuccinimides spiropentane-1 2-dicarboxylic acid monoamides diazo compounds 1 3-dipolar cycloaddition thermolysis |
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