Enantioenriched synthesis of Escitalopram using lithiation–borylation methodology

The asymmetric synthesis of Escitalopram has been completed using a lithiation–borylation reaction as the key step. Suitably functionalized enantioenriched carbamate (er 98:2) and boronic ester coupling partners were prepared and following deprotonation with s-BuLi and borylation, the tertiary alcohol was obtained in 42% yield and 93:7 er. The lithiation–borylation reaction was found to tolerate nitrile, benzylic alcohol and N-Boc functionalities. The tertiary alcohol was converted to Escitalopram in three further steps.