Addition of Me2CuLi to ortho-substituted methyl cinnamates an NMR study of the π-complex formation

Re-evaluation of Organocuprate Reactivity: Logarithmic Reactivity Profiles for Iodo- versus Cyano-Gilman Reagents in the Reactions of Organocuprates with 2-Cyclohexenone and Iodocyclohexane

“…[36] An alternative explanation based on the insertion of Cu into a syn cyclopropyl bond was proposed as part of a treatise on cuprate-cyclopropane reactivity. [37] Moreover, a Chalmers University team observed a cuprate-olefin p complex in the reaction of Me 2 CuLi with a cinnamate ester, [38] and a Bell Labs group characterized two kinds of p complexes in the reaction of this cuprate with an a-enone. [39] In the latter case it was possible to observe the appearance of enolate as the final p complex disappeared.…”

“…The NMR evidence is consistent with a fast equilibrium between starting materials (a,b-unsaturated carbonyl compound cuprate) and cuprateolefin p complexes. [38,39] Calculations suggest both monomer and dimer p complexes are feasible, [62,63] for example, in one study dimer A and heterodimer B were modeled. [63] One explanation for the lack of a TMSCl effect on the cuprate-enone reaction in ether is that dimer complex 1 b goes rapidly to enolate 1 c in the absence of a good donor ligand (L).…”

Opening the ‘black box’: oscillations in organocuprate conjugate addition reactions

“…2 Our mechanistic proposal (Scheme 1) features switching between polar and electron transfer pathways, both of which have substantial support in the literature. 8,[13][14][15] The rapid formation of de facto starting material 3?LiX from 1 and activated substrate 2?LiX [13][14][15] provides the sine qua non for an oscillating reaction: a system far from equilibrium. 1,2 In addition to dissociation (k 1 ) to the original reactants, 3?LiX can dissociate (k 2 ) to salt-free p-complex 3, 4 or it can rearrange (k 3 ) to Cu III intermediate 10, 15,16 which undergoes reductive elimination (k 6 ) to 8.…”

“…7 The second pathway involves electron transfer (ET) from Cu I reagent 1 to activated substrate 2?LiX (k 4 ) to give radical anion 11 and a Cu II species, 15 which combine in a solvent cage (k 5 ) to again arrive at common intermediate 10. The ET mechanism for organocuprate conjugate addition was championed by House, 15 but fell out of favor when p-complexes were discovered, 13,14 essentially because of Ockham's razor. 19 Our results suggest that the ET hypothesis should be revisited.…”

Re-evaluation of Organocuprate Reactivity: Logarithmic Reactivity Profiles for Iodo- versus Cyano-Gilman Reagents in the Reactions of Organocuprates with 2-Cyclohexenone and Iodocyclohexane

“…[36] An alternative explanation based on the insertion of Cu into a syn cyclopropyl bond was proposed as part of a treatise on cuprate-cyclopropane reactivity. [37] Moreover, a Chalmers University team observed a cuprate-olefin p complex in the reaction of Me 2 CuLi with a cinnamate ester, [38] and a Bell Labs group characterized two kinds of p complexes in the reaction of this cuprate with an a-enone. [39] In the latter case it was possible to observe the appearance of enolate as the final p complex disappeared.…”