1-Hexynylcopper(I)1

[33589-44-5]  · C6H9Cu  · 1-Hexynylcopper(I)  · (MW 144.70)

(coupling agent for the delivery of the 1-hexynyl group to electrophiles,2 both as such and in the form of higher order lithioorganocuprates;3 non-transferable dummy ligand used in mixed lithioorganocuprates;4 dipolarophile used in cycloaddition with nitrile oxides5)

Physical Data: yellow solid; mp 140-150 °C;6 IR (KBr) 2962, 2937, 2895, 2870, 1930, 1471, 1455, 1430, 1376, 1357, 1316, 1240, 1210, 1107, 1006, 918, 894, 781, 720, 518 cm-1.7

Solubility: sol pyridine, THF, ether; insol water. Drying: dried in vacuo at 50 °C.

Preparative Methods: addition of Copper(I) Chloride to an ammoniacal solution of 1-hexyne;8 addition of 1-hexyne to a Copper(II) Sulfate-Hydroxylamine hydrochloride mixture;2 addition of Copper(I) Iodide to 1-lithiohexyne.4

Handling, Storage, and Precautions: copper(I) salts are potentially explosive when dry; use in a fume hood.

Coupling Agent.

Hexynylcopper combines with acyl halides to yield alkynyl ketones in high yield,9 the reagent being more efficient than the corresponding organolithium and -magnesium species10 (see also Phenylethynylcopper(I) and 1-Pentynylcopper(I)). Coupling can also be achieved with aryl,2,11-13 vinyl,14 and alkyl halides,8,15 and with activated amines.16 The presence of competing functionality usually presents no problem due to the mildly nucleophilic nature of the reagent (eq 1).13

Lithioorganocuprates.

Hexynylcopper can serve as a nontransferable dummy ligand when incorporated into mixed lithioorganocuprates4,17-19 (see also 1-Pentynylcopper(I)-Hexamethylphosphorous Triamide and (3-Methoxy-3-methyl-1-butynyl)copper(I)). Thus, generation of a mixed vinylic cuprate (eq 2) allows facile vinylation of allyl bromides to proceed.4

Chemoselectivity is often observed in the delivery of the transferable group.17 Addition of a s-alkoxy transferable group to cinnamaldehyde is reported to proceed with exclusive 1,2-selectivity, and in good yield.18 Lithium bis(hexynyl)copper effectively delivers one hexynyl group to suitable electrophiles.20,21 Exclusive 1,2-addition to enals has been reported,20 and in the addition to iodoalkoxyallenes (eq 3), a good yield of the corresponding SN2 adduct is obtained.21

Higher Order Homocuprates.

Treatment of hexynyllithium with Copper(I) Iodide is reported to generate the higher order homocuprate indicated (eq 4).3,22 Regardless of composition, this species selectively and efficiently directs 1,2-addition to cyclohexenones in yields ranging from 85 to 95%.3

Cycloaddition Reactions.

Hexynylcopper has also been used as a dipolarophile in the preparation of azetidin-2-ones (eq 5).5 The cycloaddition is of note in that cis:trans adducts are formed in a 12:1 ratio (R = Ph), whereas using Phenylethynylcopper(I) as the dipolarophile the ratio is close to 1:1.

Related Reagents.

Lithium (1-Hexynyl)(2-tri-n-butylstannylvinyl)cuprate.


1. (a) Normant, J. F. S 1972, 63. (b) Sladkov, A. M.; Gol'ding, I. R. RCR 1979, 48, 868. (c) Lipshutz, B. H.; Sengupta, S. OR 1992, 41, 135. (d) FF 1977, 6, 143.
2. Castro, C. E.; Gaughan, E. J.; Owsley, D. C. JOC 1966, 31, 4071.
3. Palmisano, G.; Pellegata, R. CC 1975, 892.
4. Marino, J. P.; Floyd, D. M. JACS 1974, 96, 7138.
5. Ding, L. K.; Irwin, W. J. JCS(P1) 1976, 2382.
6. Gensler, W. J.; Mahadevan, A. P. JACS 1955, 77, 3076 and references cited therein.
7. Aleksanyan, V. T.; Garbuzova, I. A.; Gol'ding, I. R.; Sladkov, A. M. Spectrochim. Acta 1975, 31A, 517.
8. Gensler, W. J.; Mahadevan, A. P. JOC 1956, 21, 180.
9. Normant, J. F.; Bourgain, M. TL 1970, 31, 2659.
10. Bourgain, M.; Normant, J. F. BSF(2) 1973, 2137.
11. DeGraw, J. I.; Brown, V. H.; Colwell, W. T.; Morrison, N. E. JMC 1974, 17, 762.
12. Ivanchikova, I. D.; Moroz, A. A.; Shvartsberg, M. S. IZV 1991, 1447.
13. Korshunov, S. P.; Katkevich, R. I.; Vereshchagin, L. I. ZOR 1967, 3, 1327.
14. Commercon, A.; Normant, J.; Villieras, J. JOM 1975, 93, 415.
15. Bourgain, M.; Normant, J. F. BSF(2) 1973, 1777.
16. Boche, G.; Bernheim, M.; Niessner, M. AG(E) 1983, 22, 53.
17. Amos, R. A.; Katzenellenbogen, J. A. JOC 1977, 42, 2537.
18. Linderman, R. J.; McKenzie, J. R. JOM 1989, 361, 31.
19. Gordon-Gray, C. G.; Whiteley, C. G. JCS(P1) 1977, 2040.
20. Chuit, C.; Foulon, J. P.; Normant, J. F. T 1981, 37, 1385.
21. Oostveen, J. M.; Westmijze, H.; Vermeer, P. JOC 1980, 45, 1158.
22. House, H. O.; Fischer, W. F. JOC 1969, 34, 3615.

Graham B. Jones & Brant J. Chapman

Clemson University, SC, USA



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