Formation and X-ray structural determination of a diadduct obtained from (E)-l-(Phenylsulfinyl)oct-2-enyllithium and 4-t-butoxycyclopent-2-en-1-one via an unusual dianionic intermediate

Malcolm R. Binns, Richard K. Haynes, Andrew G. Katsifis, Allan H. White

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Abstract

As well as the normal vinylic sulfoxides arising by conjugate addition of each of (E)- and (Z)-l-(phenylsulfinyl)oct-2-enyllithium to 4-t-butoxycyclopent-2-en-1-one, small amounts of diadducts are also formed whenever excess lithium N, N-diisopropylamide is used to generate the octenyllithium reagents. The diadducts arise by deprotonation of the vinylic sulfoxide unit within the enolate produced in the initial conjugate addition step followed by the selective reaction of the resultant dianion with another molecule of the enone through the vinylic site. The yield of the diadduct from the carbanion of the (E)-sulfoxide can be increased dramatically through consecutive treatment of the enolate with one equivalent of butyllithium and one equivalent of the enone. The relative configuration of the diadduct from the (E)-carbanion has been established by an X-ray crystallographic study. The conformational preference of the cyclopentanone ring and the attached substituents in the diadduct is briefly discussed in the light of 400-MHz 1H n.m.r. spectroscopic and the X-ray data.

Original languageEnglish
Pages (from-to)291-301
Number of pages11
JournalAustralian Journal of Chemistry
Volume40
Issue number2
DOIs
Publication statusPublished - 1987

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