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 R• involved?

Organometallic compounds (RM, M=Li, MgBr, ZnBr, Cu(CN)Li, CuR(CN)Li-2) are oxidized with (BuOOLi)-Bu-t (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((OPr)-Pr-i)(4) + (BuOOH)-Bu-t (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 (BuOOLi)-Bu-t (method A) and Ti((OPr)-Pr-i), + (BuOOH)-Bu-t (method B) follow a S(N)2-type pathway of the nucleophile RM at the electrophilic (although anionic!) oxygen atom of (BuOOLi)-Bu-t(TiX3) to give ROM (isolated as the esters 2) with retention of configuration at R. In contrast, the oxidations with dioxygen O-2 (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)Li-2. This is due to facile electron transfer from RM to O-2 and fast isomerization (dimerization) of the intermediate radicals R degrees. The high tendency of RM cuprates, M = Cu(CN)Li, CuR(CN)Li, 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 (BuOOLi)-Bu-t (method A). (C) 2001 Elsevier Science B.V. All rights reserved.