Copper Catalyzed SN’ Reactions of Aluminum Alkyls

Wherefore Art Thou Copper? Structures and Reaction Mechanisms of Organocuprate Clusters in Organic Chemistry

“…[76] On the other hand, BF 3´E t 2 O accelerates conjugate addition [35] and alkylation of epoxides. [77] In the allylation chemistry, zinc-, [49] titanium-, [54] and aluminum- [78] based organocopper reagents show much higher S N 2' selectivity than lithium organocuprate. The Lewis acidity of the countercation to the organocuprate is undoubtedly important, but the mechanistic role still needs further studies [Eq.…”

“…[214] The S N 2 selectivity of the reaction of Bu 2 Cu(X)´2 MgBr is higher with X I, OTs than with X Cl, Br, and is also higher in ether than in THF. [203] A combination of an organocopper compound and a Lewis acid, such as RCu´BF 3 , R 2 CuLi´ZnCl 2 , [49] R 2 CuLi´Ti IV , [54] or R 2 CuLi´AlCl 3 , [78] greatly enhances the S N 2' selectivity. NMR spectroscopic studies on R 2 CuLi´ZnCl 2 and R 2 CuLi´Ti IV only showed rapid transmetalation from Cu to Zn or Ti, giving us little information on a putative Cu/Zn or Cu/Ti mixed reagent.…”

Mechanisms of Copper‐mediated Addition and Substitution Reactions

“…The S N 2 selectivity of the reaction of Bu 2 Cu(X)(MgBr) 2 is higher with X ¼ I and OTs than with X ¼ Cl and Br, and also higher in ether than in THF [111]. A combination of an organocopper compound and a Lewis acid, such as RCuÁBF 3 [5], R 2 CuLiÁZnCl 2 [112], R 2 CuLiÁTi IV [113], or R 2 CuLiÁAlCl 3 [114], greatly enhances the S N 2 0 selectivity. Cu(I)-mediated reactions of organozinc species also afford high S N 2 0 selectivities [112,[115][116][117].…”

“…BF 3 ÁEt 2 O, on the other hand, accelerates conjugate additions [31] and alkylations of epoxides and aziridines [97,127]. In allylation chemistry, zinc-based [128], titanium-based [113], and aluminum-based [114] organocopper reagents show much higher S N 2 0 selectivities than lithium cuprate does. The Lewis acidities of cuprate counter-cations are undoubtedly important, but their mechanistic roles still need further investigation (Eq.…”

Trimethylaluminum

“…Analogous reactions with allylic halides gave lower yields and selectivities [4]. Glycals react with Me 3 Al to give Cglycosides in high yields and good to excellent trans/cis ratios [5] (equation 4).…”