Selectivity in organic group transfer in reactions of mixed lithium diorganocuprates

Abstract

Solutions obtained by mixing 1 equiv of organo(ligand)copper(I) reagent (organo = n-butyl, sec-butyl, tertbutyl, phenyl, and 1-pentynyl) with 1 equiv of an organolithium reagent having a different organic group have been allowed to react with 1-bromopentane, methyl vinyl ketone, and nitrobenzene. The relative yields of products observed in these reactions of "mixed" lithium diorganocuprates, "R1R2CULÍ," are summarized and used to infer the relative reactivities of the two organic groups in these complexes. Organic moieties that form stable, unreactive, copper® compounds (1-pentynyl, tert-butoxyl, aryl) show the smallest reactivity in these cuprates and are the most generally useful first components for mixed ate complexes in which it is intended that the second component react preferentially with substrate. However, use of these groups has one drawback in reactions involving certain substrates of low reactivity: the reactivity of the second organic group in the mixed complex is significantly decreased by inclusion in the complex, relative to that which would be expected from the corresponding symmetrical cuprate. If mixed cuprates made from stable organocopper compounds show insufficient reactivity, mixed complexes containing a highly basic organic group, particularly tert-butyl, may have advantages. A survey of the relative reactivity of several alkyl bromides toward lithium di-n-butylcuprate establishes a structure-rate profile for nucleophilic coupling characteristic of an Sn2 reaction. 93 sec-C4H9 49585-84-4 23, 45I.

New Gilman-type lithium cuprate from a copper(II) salt: synthesis and deprotonative cupration of aromatics

“…Using iodine as an electrophile in the case of 2-fluoropyridine (9a) resulted in the formation of the iodide 12a 20 in a moderate 31% yield due to the concomitant formation of the 3,3 0 -dimer 13a. 32 The latter was obtained in a high 84% yield using nitrobenzene, 33 which proved to be in this reaction a better oxidant than iodine (Table 2).…”

ChemInform Abstract: 1,4‐Addition of Triorganozincates and Silyldiorganozincates to α,β‐Unsaturated Ketones.

“…Furthermore, pure 421 could be isolated from the crude product of entry 6 by TLC as above, followed by GC (column A, 130°C). (6) (according to ref. 11)): After drying over MgSO, , the crude product from entry 14 ( Table 6) was without concentration added to 76 mg (2.0 mmol) of LiAIH, in 1 ml of ether at 0 "C. After stirring at this temp.…”

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

“…The group selectivity of mixed cuprates, R 1 R 2 CuLi, is considered to be a function of R 1 E or R 2 E formation in the reductive elimination of Cu(III) intermediates, R 1 R 2 CuE, which is formed in the oxidative addition step (Scheme ). The long accepted hypothesis in substitution and 1,4‐addition of mixed diorganocuprates is that the group with a stronger CuC bond acts as the group of lower selectivity, that is, a better residual group . Theoretical studies of Nakamura established that the group selectivity is controlled by thermodynamic stability and kinetic reactivity in the reductive elimination of triorganocopper(III) intermediates formed in these reactions …”