Nucleophilic Displacements on an α-Chloro Thioether by Organocuprates: A Novel Synthesis of Desoxybiotin

Article abstract of DOI:10.1021/jo00368a007

Reactions of organometallic reagents with α-chloro thioether 2, which is readily prepared from thienoimidazolone 1, have been investigated as an approach to the synthesis of biotin (10).Methyllithium and methylmagnesium bromide attack exclusively from the less hindered exo face, affording 4, while lithium dimethylcuprate attacks from the endo face with inversion of configuration, affording 5.Lithium dipentylcuprate affords predominantly exo isomer 6, while halide-free lithium methylpentylcuprate affords predominantly endo isomer 7.Debenzylation of 7 yields desoxybiotin (9) which can be microbially oxidized to biotin (10).Alternatively, 2 was hydrolyzed and oxidized to thiolactone 13, a known precursor of biotin.