Abstract
The reaction of both cis- and trans-2,3-diphenyloxirane ( 7 and 4 , respectively) with an excess of lithium and a catalytic amount of 4,4′-di- tert-butylbiphenyl (DTBB, 2.5 mol%) in the presence of different carbonyl compounds as electrophiles (Barbier conditions) in THF at temperatures ranging between −80 and −50 °C gives the same organolithium intermediate 5 and consequently, the same 1,3-diols 6 . In the case of cis-epoxide an inversion of the configuration at the benzylic carbanionic center can explain the obtained results. Only for the dicyclopropyl ketone derivative ( 6h ) some amount (14%) of the corresponding epimer ( 6′ h ) resulting from a process with retention of the configuration of the intermediate is obtained. In representative cases, the structure of the final products ( 6 ) was unequivocally determined by X-ray diffraction analysis.
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