Reductive dearomatization of biphenyl: sequential one-pot regioselective introduction of two different electrophiles

The reaction of biphenyl (1) with an excess of lithium in THF at room temperature leads to a solution of the corresponding dianion (I), which by successive reactions with an alkyl fluoride [E₁ = n-C₈H₁₇F, c-C₅H₉CH₂F, CH₂CH(CH₂)₄F] at 0 °C and another electrophile [E₂ = n-C₄H₉Br, Et₂CO, Me₂C(O)CH₂, i-Pr₃SiCl] at −78 °C yields the corresponding 1,4-disubstituted 1,4-dihydrobiphenyls 3 in a regioselective manner, as mixtures of cis- and trans-isomers. The diastereomers of 3 are separated by column chromatography.