[43093-17-0] · C6H14CuLi · Lithium Di-n-propylcuprate · (MW 156.69)
(propylating reagent; undergoes conjugate addition reactions,1a,b,e epoxide addition reactions,1a,e substitution reactions with alkyl and vinyl substrates,1a,c,e carbocupration with alkynes,1e and acylation reactions1e)
Solubility: sol THF, Et2O.
Preparative Methods: prepared in situ from CuI salts (CuI or CuBr.SMe2) under N2 or argon atmosphere.4 Rate of cuprate formation is temperature- and CuI salt-dependent, and reagent prepared from CuI halides is critically dependent on the purity of the CuI salts used (see Lithium Dimethylcuprate for purification of CuI and CuBr).
Handling, Storage, and Precautions: stable in solution for several hours below -60 °C; cuprate reactions are generally carried out at -78 °C. Air- and moisture-sensitive; use in a fume hood.
Lithium di-n-propylcuprate displays the characteristic reactivity patterns of lithium diorganocuprates (see Lithium Di-n-butylcuprate, Lithium Dimethylcuprate, Lithium Diphenylcuprate).
n-Pr2CuLi reacts with a,b-alkenyl ketones,1e,4,5 esters,1e,6,7,8 lactones,8 and 1,3-dioxin-4-ones (eq 1)2 with 1,4-transfer of the propyl ligand. n-Pr2CuLi undergoes 1,6-addition to dienyl amides9 and 1,8-addition to trienyl ketones and esters (eq 2).10 Conjugate addition to 2-alkynoic esters proceeds in an exclusively cis manner (eq 3).11
n-Pr2CuLi participates in substitution reactions with alkyl halides1a,e,12-14 and sulfonate esters.1a,e,12a,c,d,13,15-17 Several natural product syntheses employ this coupling methodology as the key step.12,13,15-17 Vinyl iodides (eq 4)11b afford good yields of substitution products with retention of configuration. 2-Trimethylsilylpentanoyl chloride1e and g-bromobutanoyl chloride react with n-Pr2CuLi to afford the corresponding propyl ketones.
a,b-Epoxysilanes (eq 5),18 alkenyl lactones,3 and alkynyl carboxylates1e participate in anti-SN2´ pathways, although regio- and stereochemistry can vary.1 Reaction of a,b-unsaturated oxazolidines with n-Pr2CuLi (eq 6)19 also proceeds in an SN2´ manner. The steric course can be reversed and the diastereoselectivity enhanced by salt and/or solvent effects.
n-Pr2CuLi reacts with 9-Borabicyclo[3.3.1]nonane (9-BBN) to afford B-alkyl-9-BBN.20 This procedure can be extended to prepare mixed organoboranes.
Janice W. Dieter & R. Karl Dieter
Clemson University, SC, USA