1,3-Dipolar addition of diazocyclopropane to eudesmane-type methylidene lactones and thermolysis of the resulting spiro-fused pyrazolines |
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Authors: | Yu V Tomilov E V Revunov E V Shulishov V V Semenov |
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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: | Reactions of alanto-, isoalanto-, and alloalantolactones, which are unsaturated eudesmane-type lactones, with diazocyclopropane generated in situ from N-cyclopropyl-N-nitrosourea under the action of sodium methoxide proceed alike, are highly regio- and stereoselective, and always give spiro-fused pyrazolines via cycloaddition to the exocyclic double bond of the methylidene group of the lactone ring. Their thermolysis at 195?C210 °C results in elimination of molecular nitrogen, mainly yielding spiropentane-containing lactones. Minor thermolysis products (10?C12%) are isomeric 13-cyclopropyl lactones. |
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