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8.1.34.5.2 Enantioselective and Diastereoselective Intramolecular Carbolithiation

DOI: 10.1055/sos-SD-108-00276

Kizirian, J. -C.Science of Synthesis Knowledge Updates, (20122139.

Most enantioselective intramolecular carbolithiations involve an organolithium intermediate that has been previously enantiomerically enriched by enantioselective or diastereoselective deprotonation or has been prepared by tinlithium exchange from an enantiomerically pure organostannane. These kinds of reactions are detailed in Sections 8.1.34.1.6 and 8.1.34.3, respectively. However, selectivity can be generated at the carbometalation step for some substrates, examples of which are shown in Scheme 54. Lithiated species 207 and 208 are produced by lithiumbromine exchange with tert-butyllithium at low temperatures. In the case of 207, this is followed by the addition of ()-sparteine as a chiral inducer before the cyclization. The reaction occurs through a 5-exo-trig process for derivatives 207 and a 6-exo-trig process for 208.[‌255‌]

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