Lithium Diethylcuprate1

Et2CuLi

[38297-20-0]  · C4H10CuLi  · Lithium Diethylcuprate  · (MW 128.63)

(ethylating reagent; undergoes conjugate addition reactions,1a,b,d substitution reactions,1a,c,d and carbocupration1)

Physical Data: black solution (prep. from CuI).2

Solubility: sol THF, Et2O

Preparative Methods: prepared in situ from CuI salts (Copper(I) Iodide,2,3a Copper(I) Iodide-Tributylphosphine3b) under N2 or argon atmosphere (see Lithium Dimethylcuprate).

Handling, Storage, and Precautions: air- and moisture-sensitive. Use in a fume hood.

Introduction.

Lithium diethylcuprate displays the characteristic reactivity patterns of lithium diorganocuprates (see Lithium Di-n-butylcuprate, Lithium Dimethylcuprate, Lithium Diphenylcuprate).

Addition Reactions.

Lithium diethylcuprate reacts with a,b-alkenyl ketones (eq 1),1,4 esters,5 and amides6 with conjugate transfer of the ethyl ligand. Conjugate addition of Et2CuLi to the enol tosylate of an a-dione followed by elimination of the tosylate group affords the substituted a-dione (eq 2).7 The reagent adds stereoselectively (cis addition) to a,b-alkynoates8a and alkynamides (eq 3),8b affording alkenyl esters and amides.

Dienones undergo a 1,6-addition reaction.9 Reaction of Et2CuLi with thiones10 and aldehydes11 affords 1,2-addition products.

Substitution Reactions.

Lithium diethylcuprate participates in substitution reactions with alkyl halides,12 carboxylates,13 tosylate esters,2b,12a,14 sulfinate esters,15 and thioesters.9 Reaction of Et2CuLi with acyl halides16 results in nucleophilic acyl substitution, providing a useful route to ketones. Vinyl bromides17 couple with Et2CuLi to afford substitution products; the reaction proceeds with retention of configuration. Vinyl triflates18 derived from b-dicarbonyl compounds afford substitution products that may result from addition-elimination reaction pathways.

Carbocupration.

Carbocupration of alkynes with Et2CuLi affords alkenylcopper compounds which can react with alkyl halides,19 enones,20 and oxiranes21 to give substitution, 1,4-addition, and ring-opened products, respectively. Carbocupration of acetylene with Et2CuLi followed by addition of a 1-alkyne affords a dienylcuprate that can undergo reactions with various electrophiles (eq 4).22 Carbocupration of methoxyallenes has been reported.23

Miscellaneous Reactions.

Reaction of this reagent with aziridines affords ring-opened products.24 Propargylic halides (eq 5),3a a,b-alkenyl acetals,25 and vinyl lactones (eq 6)26 undergo SN2 reactions. Vinyl oxiranes27 participate in anti-stereoselective SN2 pathways. Propargylic oxiranes28 give a-allenic alcohols upon reaction with Et2CuLi.

Related Reagents.

Lithium Diethylcuprate-Tributylphosphine.


1. (a) Lipshutz, B. H.; Sengupta, S. OR 1992, 41, 135. (b) Posner, G. H. OR 1972, 19, 1. (c) Posner, G. H. OR 1975, 22, 253. (d) Faust, J.; Froböse, R. Gmelin Handbook of Inorganic Chemistry; Springer: Berlin, 1983; Copper, Part 2.
2. (a) House, H. O.; Lubinkowski, J.; Good, J. J. JOC 1975, 40, 86. (b) Johnson, C. R.; Dutra, G. A. JACS 1973, 95, 7777.
3. (a) Kalli, M.; Landor, P. D.; Landor, S. R. JCS(P1) 1973, 1347. (b) Casey, C. P.; Marten, D. F. TL 1974, 925.
4. Leland, D. L.; Polazzi, J. O.; Kotick, M. P. JOC 1981, 46, 4012.
5. (a) Fuji, K.; Tanaka, K.; Mizuchi, M.; Hosoi, S. TL 1991, 32, 7277. (b) Bernardi, A.; Cardani, S.; Poli, G.; Scolastico, C. JOC 1986, 51, 5041.
6. Meyers, A. I.; Leonard, W. R., Jr.; Romine, J. L. TL 1991, 32, 597.
7. Charonnat, J. A.; Mitchell, A. L.; Keogh, B. P. TL 1990, 31, 315.
8. (a) Walba, D. M.; Edwards, P. D. TL 1980, 21, 3531. (b) Anderson, R. J.; Corbin, V. L.; Cotterrell, G.; Cox, G. R.; Henrick, C. A.; Schaub, F.; Siddall, J. B. JACS 1975, 97, 1197.
9. Anderson, R. J.; Henrick, C. A.; Rosenblum, L. D. JACS 1974, 96, 3654.
10. Bertz, S. H.; Dabbagh, G.; Williams, L. M. JOC 1985, 50, 4414.
11. Singh, S. M.; Oehlschlager, A. C. CJC 1988, 66, 209.
12. (a) Bajgrowicz, J. A.; El Hallaoui, A.; Jacquier, R.; Pigiere, C.; Viallefont, P. TL 1984, 25, 2759. (b) Bajgrowicz, J. A.; El Hallaoui, A.; Jacquier, R.; Pigiere, C.; Viallefont, P. TL 1984, 25, 2231. (c) Lion, C.; Dubois, J.-E. T 1975, 31, 1223.
13. Casey, C. P.; Marten, D. F.; Boggs, R. A. TL 1973, 2071.
14. (a) Bajgrowicz, J. A.; El Hallaoui, A.; Jacquier, R.; Pigiere, C.; Viallefont, P. T 1985, 41, 1833. (b) Mori, K.; Sugai, T. S 1982, 752.
15. Harpp, D. N.; Vines, S. M.; Montillier, J. P.; Chan, T. H. JOC 1976, 41, 3987.
16. (a) Rossi, R.; Carpita, A.; Cossi, P. T 1992, 48, 8801. (b) Coutrot, P.; Ghribi, A. S 1986, 661.
17. Miller, R. B.; McGarvey, G. JOC 1979, 44, 4623.
18. Kant, J.; Sapino, C., Jr.; Baker, S. R. TL 1990, 31, 3389.
19. Germon, C.; Alexakis, A.; Normant, J. F. S 1984, 40.
20. Alexakis, A.; Berlan, J.; Besace, Y. TL 1986, 27, 1047.
21. Alexakis, A.; Cahiez, G.; Normant, J. F. T 1980, 36, 1961.
22. Furber, M.; Taylor, R. J. K.; Burford, S. C. JCS(P1) 1986, 1809.
23. Alexakis, A.; Normant, J. F. Isr. J. Chem. 1984, 24, 113.
24. Tanner, D.; Somfai, P. T 1988, 44, 619.
25. Ghribi, A.; Alexakis, A.; Normant, J. F. TL 1984, 25, 3079.
26. MacMillan, J.; Taylor, D. A. JCS(P1) 1985, 837.
27. Marshall, J. A.; Crute, T. D., III; Hsi, J. D. JOC 1992, 57, 115.
28. Alexakis, A.; Marek, I.; Mangeney, P.; Normant, J. F. T 1991, 47, 1677.

Shou-Yuan Lin & R. Karl Dieter

Clemson University, SC, USA



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