Dilithium Tributylcuprate


[61288-01-5]  · C12H27CuLi2  · Dilithium Tributylcuprate  · (MW 248.77)

(organometallic butylating agent for ketones,1 enol ethers,2 and organomercurials3)

Physical Data: in ether, 1H NMR spectra have shown4 that Li2CuBu3 is not an actual species, but a more complex mixture that can be more accurately represented as a BuLi to BuCu ratio. In pentane, however, Li2CuBu3 exists in equilibrium with BuLi and LiCuBu2 (see Dilithium Trimethylcuprate).

Solubility: sol ether, THF, and pentane to -80 °C.

Preparative Method: n-Butyllithium (3.3 mmol) is added to Copper(I) Iodide (1.0 mmol) in ether at -40 °C.

Handling, Storage, and Precautions: Li2CuBu3 should be used as soon as possible following preparation. Use in a fume hood.

Addition to Ketones and Enol Ethers.

Li2CuBu3 behaves similarly to Li2CuMe35 in enhancing the yield and stereoselectivity in reactions with ketones (eq 1)2 (see Dilithium Trimethylcuprate). Notable in additions to hindered ketones is a depression of carbonyl reductions with Li2CuBu3 compared to the alkyllithium reagent.

Li2CuBu3 undergoes reaction with 2,3-dihydrofuran to yield 3-octen-1-ol in 75% yield.2 The optimal conditions for reaction use 5.0 equiv of butyllithium per 1.0 equiv CuI. This result raises the possibility that the reactive agent may be a cuprate species possessing a Bu:Cu ratio that is >3 (eq 2).4,6

Alkylation of Organomercurials.

Butylation of alkenyl-, phenyl-, and alkylmercurials with Li2CuBu3 proceeds only in moderate yield (40-60%), but nonetheless exhibits an almost tenfold enhancement in yield over that obtained with LiCuBu2.3

1. Macdonald, T. L.; Still, W. C. JACS 1975, 97, 5280.
2. Fujisawa, T.; Kurita, Y.; Kawashima, M.; Sato, T. CL 1982, 1641.
3. Larock, R. C.; Leach, D. R. OM 1982, 1, 74.
4. San Fillippo, J. IC 1978, 17, 275.
5. Macdonald, T. L.; Still, W. C. TL 1976, 31, 2659.
6. Lipshutz, B. H.; Kozlowski, J. A.; Breneman, C. M. JACS 1985, 107, 3197.

Timothy J. Guzi & Timothy L. Macdonald

University of Virginia, Charlottesville, VA, USA

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