Oxidation of organometallic compounds (RM, M=Li, MgBr, ZnBr, CuCNLi, Cu(R)CNLi2) with tBuOOLi, Ti(OiPr)4- mediated with tBuOOH, and with O2, to give alcohols (ROH). Are radicals Rradical dot involved?

Organometallic compounds (RM, M=Li, MgBr, ZnBr, Cu(CN)Li, CuR(CN)Li2) are oxidized with tBuOOLi (or PhCMe2OOLi) (method A) to the corresponding alcohols (ROH), in good to very good yields. This oxidation works also well with the protic system Ti(OiPr)4+tBuOOH (method B) in the case of RM, M=Li, MgBr and ZnBr. Stereochemical studies with the configurationally stable cis- and trans-cyclopropyl metal compounds, cis- and trans-1-M, respectively, show that the reactions of RM, M=Li, MgBr, with tBuOOLi (method A) and Ti(OiPr)4+tBuOOH (method B) follow a SN2-type pathway of the nucleophile RM at the electrophilic (although anionic!) oxygen atom of tBuOOLi(TiX3) to give ROM (isolated as the esters 2) with retention of configuration at R. In contrast, the oxidations with dioxygen O2 (method C) occur with loss of stereochemistry in the cyclopropyl alcohols ROH (RM, M=Li, MgBr), and additional formation of cyclopropyl dimers R–R 3 in the case of RM, M=Cu(CN)Li, CuR(CN)Li2. This is due to facile electron transfer from RM to O2 and fast isomerization (dimerization) of the intermediate radicals Rradical dot. The high tendency of RM cuprates, M=Cu(CN)Li, CuR(CN)Li2, for electron transfer reactions is also indicated by some loss of stereospecificity in the formation of ROH, and some dimer 3 formation, even with the oxidant tBuOOLi (method A) .