[21500-57-2] · C6H10CuLi · Lithium Diallylcuprate · (MW 152.63)
Alternate Name: lithium di(2-propenyl)cuprate.
Physical Data: 13C NMR d 150, 91, 24.2b
Solubility: sol THF, Et2O.
Preparative Methods: prepared in situ from CuI salts (Copper(I) Iodide2a,3a or CuI.SBu23b) under N2 or argon atmosphere (see Lithium Dimethylcuprate) and Allyllithium3a,3c which is prepared from Allyltributylstannane or Tetraallylstannane and Phenyllithium or n-Butyllithium.
Handling, Storage, and Precautions: air- and moisture-sensitive. Use in a fume hood.
Lithium diallylcuprate displays the characteristic reactivity patterns of lithium diorganocuprates (see e.g. Lithium Di-n-butylcuprate, Lithium Dimethylcuprate, Lithium Diphenylcuprate). The very high reactivity of (CH2=CHCH2)2CuLi is sometimes problematic, and allylcopper reagents can be more effective (see Allylcopper).3a
Lithium diallylcuprate reacts with a,b-alkenyl ketones (eq 1),1,9 lactones,4 esters,5 nitriles,6 lactams (eq 2),7 and phosphonates8 with conjugate transfer of the allyl ligand. Addition of Chlorotrimethylsilane can accelerate the conjugate addition reaction and results in improved yields.9
The reagent adds stereoselectively (cis addition) to a,b-alkynoates, affording 2,5-dienoates (eq 3).10 Dienyl esters and dienyl nitriles exclusively afford 1,6-addition products in good yields.6 Diethyl 2-vinyl-1,1-cyclopropanedicarboxylate gives mixtures of 1,5- and 1,7-addition products.11 Tandem conjugate addition-enolate trapping is a powerful synthetic method, although additives12 and solvent changes are sometimes required. Conjugate addition of the reagent to ketoketenimines affords b-enamino ketones under mild reaction conditions.13 1-Alkoxycarbonylpyridinium halides undergo both 1,2- and 1,4-addition reactions, leading to regioisomeric dihydropyridines (eq 4).14 Lithium diallylcuprate reacts with a,b-enals in the presence15 of TMSCl to give the 1,2-addition products regioselectively.
Lithium diallylcuprate participates in substitution reactions with alkyl halides,2a carboxylates,16 and sulfonate esters.17 Secondary tosylates undergo the substitution reaction with clean inversion of configuration; the reaction is greatly facilitated when a heteroatom (e.g. O, S) is proximate to the nucleofugal substituent and elimination pathways are minimized (eq 5).18 4-Bromo-2-butenyltributylphosphonium salts undergo substitution reactions with the reagent, with formation of an ylide which can react with aldehydes to afford dienes.19 Allylic ammonium salts participate in syn-SN2´ pathways with good stereo- and regioselectivity (eq 6).20
1-Cyclooctenyl phenyl sulfones fail to undergo conjugate addition with lithium diallylcuprate, instead affording reduction products.21
Shou-Yuan Lin & R. Karl Dieter
Clemson University, SC, USA