Gas-Phase Reactivity of Group 11 Dimethylmetallates with Allyl Iodide

Abstract

Copper-mediated allylic substitution reactions are widely used in organic synthesis, whereas the analogous reactions for silver and gold are essentially unknown. To unravel why this is the case, the gas-phase reactions of allyl iodide with the coinage metal dimethylmetallates, [CH(3)MCH(3)](-) (M = Cu, Ag and Au), were examined under the near thermal conditions of an ion trap mass spectrometer and via electronic structure calculations. [CH(3)CuCH(3)](-) reacted with allyl iodide with a reaction efficiency of 6.6% of the collision rate to yield: I(-) (75%); the cross-coupling product, [CH(3)CuI](-) (24%); and the homo-coupling product, [C(3)H(5)CuI](-) (1%). [CH(3)AgCH(3)](-) and [CH(3)AuCH(3)](-) reacted substantially slower (reaction efficiencies of 0.028% and 0.072%). [CH(3)AgCH(3)](-) forms I(-) (19%) and [CH(3)AgI](-) (81%), while only I(-) is formed from [CH(3)AuCH(3)](-). Because the experiments do not detect the neutral product(s) formed, which might otherwise help identify the mechanisms of reaction, and to rationalize the observed ionic products and reactivity order, calculations at the B3LYP/def2-QZVP//B3LYP/SDD6-31+G(d) level were conducted on four different mechanisms: (i) S(N)2; (ii) S(N)2'; (iii) oxidative-addition/reductive elimination (OA/RE) via an M(III) η(3)-allyl intermediate; and (iv) OA/RE via an M(III) η(1)-allyl intermediate. For copper, mechanisms (iii) and (iv) are predicted to be competitive. Only the Cu(III) η(3)-allyl intermediate undergoes reductive elimination via two different transition states to yield either the cross-coupling or the homo-coupling products. Their relative barriers are consistent with homo-coupling being a minor pathway. For silver, the kinetically most probable pathway is the S(N)2 reaction, consistent with no homo-coupling product, [C(3)H(5)AgI](-), being observed. For gold, no C-C coupling reaction is kinetically viable. Instead, I(-) is predicted to be formed along with a stable Au(III) η(3)-allyl complex. These results clearly highlight the superiority of organocuprates in allylic substitution reactions.

Tandem Gold Self‐Relay Catalysis for the Synthesis of 2,3‐Dihydropyridin‐4(1 H)‐ones: Combination of σ and π Lewis Acid Properties of Gold Salts

“…The NBO charges of the C1, C2, and C3 atoms change only relatively little during the whole process. This suggests that the oxidation of the Cu atom in [( i Pr) 2 Cu] − (from Cu I to Cu III ) mainly takes place during the binding of [( i Pr) 2 Cu] − to the allylic substrate, rather than during the dissociation step,35, 36 whereas the reduction of the S atom of the phosphorothioate ester mainly takes place during the dissociation step, and the C1C2C3 chain plays a role in the process of the electron transfer.…”

Formation of Grignard Reagent-like Complex [CH3–M–I]− via Oxidative Addition of CH3I on Coinage Metal Anions M− (M = Cu, Ag, Au) in the Gas Phase

“…79 For instance, the reaction of dimethylmetallates [CH 3 MCH 3 ] ¹ (M = Cu, Ag) with allyl iodide (CH 2 =CHCH 2 I) yields CH 3 C 3 H 5 via cross-coupling reaction. 7 Recently, we found that methyl iodide (CH 3 I) undergoes oxidative addition to Au ¹ to yield [CH 3 AuI] ¹ , where an Au atom is inserted into the carboniodine (CI) bond of CH 3 I. 10 We further proposed based on theoretical calculations that the oxidative addition proceeds via nucleophilic attack by Au ¹ on CH 3 I, followed by migration of the leaving I ¹ to Au.…”

Ate Complexes in Iron‐Catalyzed Cross‐Coupling Reactions

“…[6,7] Moreover,gas-phase fragmentation experiments on the mass-selected ions provide unique information on their microscopicr eactivity. [6][7][8][9] As am odel system, we chose the reaction between PhMgCl and iPrCl in THF with the commonly employed Fe(acac) 3 as ac atalyst precursor and investigated the effect of various additives and ligands. [2] Negative-ionm ode ESI mass spectra of solutions of Fe(acac) 3 treated with 1-3 equiv of PhMgCl showedt he reduction of the Fe III precursor to an Fe II species (Figure S1-S3 in the Supporting Information), which is in line with previous reports.…”