On the nature of the chain-extending species in organolithium initiated stereospecific reagent-controlled homologation reactions using α-chloroalkyl aryl sulfoxides
作者:Amanda L. Hoyt、Paul R. Blakemore
DOI:10.1016/j.tetlet.2014.08.123
日期:2015.6
The reaction of an organolithium with an alpha-chloroalkyl aryl sulfoxide ostensibly generates an alpha-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*, 5R*)-4,5-diphenyl-1,3,2-dioxaborolane was homologated by treatment with scalemic (S)-chloromethyl phenyl sulfoxide and n-BuLi (THF, -78 degrees 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. (C) 2014 Elsevier Ltd. All rights reserved.