[53093-27-9] · C4H10CuLi · Lithium n-Butyl(hydrido)cuprate · (MW 128.63)
(in situ hydrido copper reagent; reductive removal of halogen, mesyloxy, or tosyloxy groups; reduction of aldehydes or ketones to alcohols; 1,4-reduction of enones2)
Preparative Method: copper(I) hydride (4 mmol, prepared by the method of Whitesides3) is placed in a round-bottom flask at -50 °C under an inert atmosphere, washed with -50 °C ether (4 times), and then treated with -40 °C ether before the addition of cold n-Butyllithium in hexane (4 mmol); the resulting dark brown solution (reagent partially insoluble) is stirred for 10 min, an ethereal solution of the substrate (1 mmol) is added, and the reaction mixture is allowed to warm to rt; after 2 h stirring time, the mixture is poured into saturated aqueous ammonium chloride solution, the aqueous phase is extracted with ether, and the combined organic phase is dried.2
Primary, secondary, and tertiary halides as well as mesylates and tosylates are reduced by lithium butyl(hydrido)cuprate in 70-100% yield (Table 1). Although aldehydes and ketones are reduced to their corresponding alcohols, a,b-unsaturated ketones are only reduced to their ketones (eqs 1-3). The n-butyl group is not incorporated into the product.
ate complexes of the general formula LiCuHR (where R = t-Bu,2 i-Pr,2 1-pentynyl,2,4 O-t-butyl,4 or PhS4) were prepared. The n-butyl
ate complex is the most reactive hydride reducing agent. The use of THF as solvent provides no advantage,2 whereas THF/HMPA is an effective solvent.4
For a discussion of alternative methods for reductive removal of halogen, hydroxy, mesyloxy, or tosyloxy groups, see Copper(I) Iodide-Lithium Trimethoxyaluminum Hydride.
For a discussion of alternative methods for reduction of aldehydes or ketones to alcohols, see Lithium Aluminum Hydride and related reagents, or Sodium Borohydride and related reagents.
For a discussion of alternative methods for 1,4-reduction of enones, see Copper(I) Bromide-Sodium Bis(2-methoxyethoxy)aluminum Hydride.
Ronald K. Russell
The R. W. Johnson Pharmaceutical Research Institute, Raritan, NJ, USA