The reaction of an organolithium with an α-chloroalkyl aryl sulfoxide ostensibly generates an α-chloroalkyllithium by sulfoxide-lithium exchange, but the actual identity of the chain-extending species in chlorosulfoxide-based StReCH reactions is not certain. To explore this issue, racemic 2-cyclohexyl (4R<sup>∗</sup>,5R<sup>∗</sup>)-4,5-diphenyl-1,3,2-dioxaborolane was homologated by treatment with scalemic (S)-chloromethyl phenyl sulfoxide and n-BuLi (THF, -78 °C). The reaction proceeded without a detectable level of kinetic resolution, a finding consistent with chloromethyllithium being the active chain-extending species rather than a chiral sulfurane intermediate.
Hoyt, A. L., & Blakemore, P. R. (2015). On the nature of the chain-extending species in organolithium initiated stereospecific reagent-controlled homologation reactions using α-chloroalkyl aryl sulfoxides. Tetrahedron Letters, 56(23), 2980–2982. https://doi.org/10.1016/j.tetlet.2014.08.123