Lithium cyclopropylcuprate

The route to cyclopentanes via thermolysis of vinylcyclopropanes is an attractive one, limited only by the availability of the vinylcyclopropane. Trost s use of (32) offers one solution to this problem, but in related investigations Piers et and also Marino and Browne, have demonstrated that the vinylcyclopropanes are smoothly produced by reaction between lithium cyclopropylcuprates (37) and jS-halogeno-ajS-unsaturated ketones, according to Scheme 13. Furthermore, Marino and Browne have found that conjugate addition of (37) to acetylenic ketones offers additional scope for the synthesis of monocyclic vinylcyclopropanes, e.g. (38) (39). 

The related lithium(phenylthio)cyclopropylcuprate, prepared from cyclopropyllithium and PhSCu, has been extensively used in the synthesis of /1-cyclopropyl enones by coupling with the corresponding fl-iodo enones (equation 10)34 36. Repetitive regioselective coupling of ethynylcyclopropane units by this method led to polyspirocyclopropyl acetylenes as precursors to [NJpericyclynes37. 

When monosubstituted ketals 18 are used, the addition of lithium dialkylcuprates mainly yields the cyclopropylcuprates with a newly created quaternary center, namely 19A, in 90-100 /o selectivity. ... 

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