# Reaction mechanism of lithiated benzene and oxygen in acid

According to (1) addition of O2 in acid to lithiated benzene makes phenol.

I'm trying to deduce the mechanism, and somehow it doesn't feel right but I'm not sure.

(1) Snieckus, V. Directed ortho metalation. Tertiary amide and O-carbamate directors in synthetic strategies for polysubstituted aromatics. Chem. Rev. 1990, 90 (6), 879–933. DOI: 10.1021/cr00104a001.

• Addition of oxygen followed by acid work up, not oxygen in acid – Waylander Dec 27 '19 at 19:44
• Your proposed mechanism doesn't quite work; loss of H2O would lead to a six-electron oxygen species (that should already set off alarm bells), and to get back its octet, that oxygen would have to pick up the equivalent of a hydride, not a proton (from water). Based on the original paper pubs.acs.org/doi/abs/10.1021/jo00380a034 that Snieckus cites there isn't any attempt to generate singlet O2, so I imagine that the mechanism is (at least partly) radical, but I don't have a concrete suggestion in mind. – orthocresol Dec 28 '19 at 1:04
• In addition, @Waylander's comment is a very salient point which you should pay more attention to, imo: it is oxygen followed by acid, not at the same time (that would be rather pointless, as adding any kind of acidic solution - $\ce{O2}$ or not - to an organolithium would simply protonate it). So we presumably need to react $\ce{ArLi}$ with $\ce{O2}$ (with a radical mechanism) to get to a phenoxide $\ce{ArO-}$, which upon workup forms the phenol $\ce{ArOH}$. Not trivial... – orthocresol Dec 28 '19 at 1:07
• @orthocresol: There is the possibility that the aryl hydroperoxide generated during workup oxidizes TMEDA. but I am not convinced. – user55119 Dec 28 '19 at 2:33