Allenes are an important class of unsaturated molecules that may exhibit axially chirality; however, existing methods for their enantioselective synthesis are either circuitous or limited in scope with regard to substitution level. It was recently reported that alkenes can be prepared in a stereospecific manner by an eliminative cross-coupling process involving pairs of distinct stereodefined (i.e., enantioenriched) sp3-hybridized carbenoids. A related stereospecific connective synthesis of allenes has now been realized involving eliminative cross-coupling between stereodefined sp3- and sp2-hybridized carbenoids. For example, the (E)-configured alpha-sulfonylvinylcopper alkylidene carbenoid generated by carbocupration of PhCCSO2pTol with BuCu, reacted with a lithiated carbamate alkyl carbenoid [(S)-1-[(diisopropylamino)carbonyloxy]-1-phenylethyllithium] to yield the expected tetrasubstituted allene PhBuC=C=CPhMe. Our ongoing efforts to optimize this allene synthesis and to quantify the effect of substitutions on yield and the level of stereochemical fidelity, will be described.

Stereospecific connective synthesis of allenes by eliminative cross-coupling of stereodefined sp3- and sp2-hybridized carbenoids

2019 Spring National Meeting

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