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.