Unusual Homocoupling in the Reaction of Diorganocuprates with an Allylic Halide

Abstract

The reactions of dialkyl-and diarylcuprates (R 2 CuM; M ) Li, MgBr) with perfluoroallyl iodide were found to giVe the homocoupling products R-R as the only product of C-C bond formation. Density functional calculations reVealed that the perfluoroallyl ligand, being strongly electron-withdrawing and less Lewis basic, significantly changes the electronic properties of the allylcopper(III) intermediate and acts as a spectator ligand in the reductiVe elimination.

Theoretical Insights into Enantioselective Catalysis: The Mechanism of the Kharasch–Sosnovsky Reaction

“…Interestingly, a significant tilt in the cyclohexenyl group can be observed in a front view in such way that this ligand is oriented towards the non‐hindered quadrants7 of the mebox ligand, similar experimental data were found for an η 3 ‐cyclohexenyl–palladium(II) complex bearing a C 2 ‐symmetric ligand 58. Free energy calculations on the allyl‐copper(III) key reaction intermediate show that η 1 ‐coordination is preferred over η 3 ‐coordination by 7.6 kcal mol −1 (Figure 11), a situation in qualitative agreement with previous calculations on some allyl‐copper(III) derivatives 23…”

“…[58] Free energy calculations on the allyl-copperA C H T U N G T R E N N U N G (III) key reaction intermediate show that h 1 -coordination is preferred over h 3coordination by 7.6 kcal mol À1 (Figure 11), a situation in qualitative agreement with previous calculations on some allyl-copperA C H T U N G T R E N N U N G (III) derivatives. [23] Both calculated TSs for the reactions connecting the Figure 12) indicate a clear preference for the path involving migration (7.5 kcal mol À1 , Figure 12) rather than retention (17.7 kcal mol À1 , Figure 13) of the C=C bond.…”

“…Such a reaction mechanism is analogous to the pathways invoked to explain the results on regio‐ or stereoselectivity on several kinds of reactions involving allyl‐copper(III) reaction intermediates 21. Furthermore, theoretical calculations have indicated that allyl‐copper(III) compounds can adopt both η 1 ‐ and η 3 ‐coordination types, which can readily interconvert,22, 23 (in a similar way to the well‐known η 3 →η 1 →η 3 isomerization of allyl‐palladium complexes) 24…”

“…Such a reaction mechanism is analogous to the pathways invoked to explain the results on regio-or stereoselectivity on several kinds of reactions involving allyl-copperA C H T U N G T R E N N U N G (III) reaction intermediates. [21] Furthermore, theoretical calculations have indicated that allyl-copperA C H T U N G T R E N N U N G (III) compounds can adopt both h 1 -and h 3 -coordination types, which can readily interconvert, [22,23] (in a similar way to the well-known h 3 !h 1 !h 3 isomerization of allyl-palladium complexes). [24] Interestingly, experimental studies on the vinylic/allylic scrambling in Kharasch-Sosnovsky reactions show different results depending on the particular reaction conditions.…”

Regioselective CF Bond Activation of Hexafluoropropylene on Palladium(0): Formation of a Cationic η2‐Perfluoroallylpalladium Complex

“…Although a limited number of transition metal mediated or catalyzed CÀF bond-activation reactions of 1 have been reported, [5,6] no active species capable of recognizing different types of fluorines and cleaving them chemoselectively, has been developed. In addition, the product that would be generated from the C(sp 3 ) À F bond cleavage of 1 on palladium is expected to be a perfluoroallylpalladium complex, [7,8] and the coordination mode as well as the fluxional behavior of the perfluoroallyl ligand on palladium is of great interest especially as a comparison to the well-known allylpalladium species. [9] Herein, we report the novel regioselective C À F bond-cleavage reactions of 1 with zero-valent palladium in the presence of coadditives.…”