A general synthesis of methylenecyclopentanes by a stereoselective [3 + 2] approach

Eugene Ghera, Tamar Yechezkel, Alfred Hassner

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Abstract

The [3 + 2] cyclopentanation involving 3-(phenylsulfonyl)-2-(bromomethyl)-1-propene (1) and representative (E) α,β-unsaturated acyclic esters and ketones has been studied. High yields and complete stereoselectivity were observed in all reactions leading to tri- or tetrasubstituted methylenecyclopentanes. The anti-diastereoselectivity in the first, Michael addition step is rationalized by a chelation-controlled transition state in which MO interactions of the two π systems are involved. The Michael reactions of methallyl sulfone 8 with (E) enoates in the absence and presence of HMPA confirms the influence of chelation on the diastereomeric ratio of adducts. Cyclopentanations involving 1 with cyclohexenone, 2(5H)-furanone, and 5,6-dihydro-2-pyranone, respectively, were also studied with emphasis on the factors influencing the stereochemical outcome of the annulation process.

Original languageEnglish
Pages (from-to)4959-4966
Number of pages8
JournalJournal of Organic Chemistry
Volume61
Issue number15
DOIs
StatePublished - 26 Jul 1996

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