Reactivity of mixed organozinc and mixed organocopper reagents: 11. Nickel‐catalyzed atom‐economic aryl–allyl coupling of mixed (n‐alkyl)(aryl)zincs

Abstract

Group selectivity in the allylation of mixed (n-butyl)(phenyl)zinc reagent can be controlled by changing reaction parameters. CuCN-catalyzed allylation in tetrahydrofuran (THF)-hexamethylphosphoric triamide is n-butyl selective and also γ-selective in the presence of MgCl 2 , whereas CuI-catalyzed allylation in THF in the presence of n-Bu 3 P takes place with a n-butyl transfer:phenyl transfer ratio of 23:77 and an α:γ transfer ratio of phenyl of 76:24. NiCl 2 (Ph 3 P) 2 -catalyzed allylation in the presence of LiCl is phenyl selective with an α:γ ratio of 65:35. The reaction of methyl-or n-butyl(aryl)zinc reagents with an allylic electrophile in THF at room temperature in the presence of NiCl 2 (Ph 3 P) 2 catalyst and LiCl as an additive provides an atom-economic alternative to aryl-allyl coupling using diarylzincs.The ratio of GC yields of 6a and 7a. e The ratio of GC yields of 6b and 7b. f Stoichiometric cuprate reagent derived from n-BuPhZn and CuI (or CuCN) was prepared in situ. g X = Cl, Br and SCN. h X = Cl, OAc, OTf and acac. /journal/aoc d The ratio of GC yields of (6a + 7a) and (6b + 7b). e The ratio of GC yields of 6a and 7a. f The ratio of GC yields of 6b and 7b.The ratio of GC yields of (6a + 7a) and (6b + 7b). e The ratio of GC yields of 6a and 7a. f The ratio of GC yields of 6b and 7b.Reactivity of mixed organozinc and mixed organocopper reagents: 11

Reactivities of mixed organozinc and mixed organocopper reagents. Part 13 Kinetic study for phosphine‐catalyzed acylation of alkylarylzincs and effect of residual group on the transfer rate of alkyl group

“…In their systematic work, Erdik and coworkers observed that the group selectivities of mixed diorganocuprates, R 1 R 2 CuM (MMgBr), ZnI, diorganozincs, R 1 R 2 Zn, and Cu‐catalyzed mixed triorganozincates, R 1 (R 2 ) 2 ZnMgBr, depend on the reaction parameters, that is, the electrophilic substrate, the solvent, and the temperature as well as the transition metal catalyst and organocatalyst, and reported that the group selectivity of mixed organocopper and organozinc reagents can be controlled by changing the reaction parameters. They also developed new atom‐economic synthetic procedures for CC, C‐acyl, and CN coupling employing mixed arylzinc reagents. However, probing the origin of group selectivity in the mixed organocopper and organozinc reagents still seems a problem.…”

“…However, in the reactions of R 2 CuM, R 2 Zn, and R 3 ZnM reagents, a synthetic problem arises because only one of the R groups can be transferred to the electrophile. This limitation to the atom‐economic use of R 2 CuM, R 2 Zn, and R 3 ZnM reagents has been solved by using either (i) mixed organocopper and organozinc reagents of R 1 R 2 CuM, R 1 R 2 Zn, and (R 1 ) 2 R 2 ZnM type, in which the R 2 group has a lower transfer rate than R 1 group, or (ii) mixed organocopper and organozinc reagents of R R R T CuM, R R R T Zn, and (R R ) 2 R T ZnM type, in which R R is residual (dummy) group and R T is transferable group.…”