Synthesis of Sulfur Enriched Cyclohexenes via the Tungsten-Promoted Dearomatization of a Phenyl Sulfone.

Prior work with the dearomatization agent [WTp(NO)(PMe3)] (Tp = trispyrazolylborate) has demonstrated the ability to synthesize cis, cis-3,4,6 trisubstituted cyclohexenes from phenyl sulfones. Herein, the compatibility of these methods with sulfur nucleophiles was investigated for the synthesis of sp3-enriched thioether- and thioacetate-functionalized cyclohexenes. Protonation of the WTp(NO)(PMe3)(η 2-PhSO2Me) complex followed by addition of a sulfur nucleophile was only successful for a thioacetate salt. However, when the first nucleophile was an ester enolate, subsequent protonation and nucleophilic addition successfully yielded a range of cyclohexene complexes with thioacetate, thiol, and sulfonyl substituents. Oxidative decomplexation of these complexes liberated the corresponding cyclohexene products. This strategy was then applied to the synthesis of a thioglycolate ester functionalized tetrahydrophenanthridinone.