Oxidation of organometallic compounds (RM, M = Li, MgBr, ZnBr, CuCNLi, Cu(R)CNLi2) with (BuOOLi)-Bu-t, Ti((OPr)-Pr-i)(4)-mediated with (BuOOH)-Bu-t, and with O-2, to give alcohols (ROH). Are radicals R-center dot 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 wel l 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 configu rationally stable cis- and trans-cyclopropyl metal compounds, cis- and tran s-1-M, respectively, show that the reactions of RM, M = Li, MgBr, with (BuO OLi)-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 an ionic!) oxygen atom of (BuOOLi)-Bu-t(TiX3) to give ROM (isolated as the est ers 2) with retention of configuration at R. In contrast, the oxidations wi th dioxygen O-2 (method C) occur with loss of stereochemistry in the cyclop ropyl alcohols ROH (RM, M = Li, MgBr), and additional formation of cyclopro pyl 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 (dimeriza tion) of the intermediate radicals R degrees. The high tendency of RM cupra tes, M = Cu(CN)Li, CuR(CN)Li, for electron transfer reactions is also indic ated by some loss of stereospecificity in the formation of ROH, and some di mer 3 formation, even with the oxidant (BuOOLi)-Bu-t (method A). (C) 2001 E lsevier Science B.V. All rights reserved.