Homo- and Hetero-oxidative
Coupling of Benzyl Anions
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Abstract
The regioselective benzylic metalation of substituted
toluenes using BuLi/KO-<i>t</i>-Bu/TMP(H) (LiNK metalation
conditions) with subsequent in situ oxidative C–C coupling
has been developed for the facile generation of 1,2-diarylethanes.
A range of oxidants can be used for the oxidative coupling step, with
1,2-dibromoethane proving optimal. Heterocouplings can be achieved
starting from a mixture of two different toluenes with a bias toward
cross coupling achievable by using a 2-fold excess of one toluene
starting material. The utility of this approach is illustrated by
the synthesis of several biologically active natural products. A distinct
advantage is that the synthetic steps typically required to preactivate
the coupling substrates are eliminated and no transition metal is
required to facilitate the C–C bond formation