Sulfones as Synthetic Linchpins: Transition-Metal-Free sp3 -sp2 and sp2 -sp2 Cross-Couplings Between Geminal Bis(sulfones) and Organolithium Compounds.

ABSTRACT

A valuable umpolung strategy that highlights the ambiphilic nature of the bis(phenylsulfonyl)methyl synthon and demonstrates its utility as a synthetic linchpin is reported. Although the bis(phenylsulfonyl)methyl group is typically introduced as an sp3 -carbon nucleophile, it is demonstrated that it can also function as an effective sp2 -carbon electrophile in the presence of organolithium nucleophiles. Alkyl- and aryllithiums couple with the central carbon of the bis(phenylsulfonyl)methyl unit to ultimately generate trisubstituted alkenes, comprising formal sp3 -sp2 and sp2 -sp2 cross-couplings between organolithium reagents and bis(sulfones). This process occurs almost instantaneously at -78 °C in the absence of any transition metals. By developing this curious transformation, it has been demonstrated that bis(phenylsulfonyl)methane is a valuable synthetic linchpin, which can undergo two C-C bond-forming processes as an sp3 -nucleophile, followed by a third C-C bond-forming reaction as an effective sp2 -electrophile. This discovery significantly enhances the utility of this ubiquitous, but underutilized, linker group.