[51760-92-0]  · C3H3Li  · Allenyllithium  · (MW 45.99)

(allows the preparation of functionalized monosubstituted allenes1-3 and conjugated allenic ketones;4 adds regioselectively to vinyl epoxides5,6)

Physical Data: 13C NMR solution data in THF7 have been reported. Allenyllithium solutions show a strong IR absorption8 at 1885 cm-1.

Solubility: at -60 °C, allenyllithium is slightly sol THF-hexane (1:1) but sol ether-THF.9

Form Supplied in: prepared in situ and used directly.

Preparative Methods: in situ under nitrogen by reaction of n-Butyllithium in hexane with Allene in THF at -65 °C for 10 min,8-10 or from Bromoallene by metal-halogen exchange.10

Handling, Storage, and Precautions: solutions are unstable and should be kept below -60 °C.3b

This reagent adds to a variety of electrophiles to give allenic and/or alkynic compounds depending on both the substrate and the solvent used.

Addition to Halides.

In THF solution, allenyllithium reacts readily with alkyl halides10 at low temperature to afford mainly monosubstituted allenes along with some alkynic compounds (easily removed by AgNO3 treatment). Addition of 1 equiv. of Hexamethylphosphoric Triamide suppresses the formation of alkynes.1,11 Alkylation with functionalized halides has been studied.2,3 Addition to 1-iodo-2-trimethylsilylethane leads to b-allenylsilane in good yield (eq 1).2 g-Chloroallene is easily accessible by alkylation with 1-bromo-3-chloropropane (eq 2).3

Condensation of the reagent with Chlorotrimethylsilane leads to a mixture of silylated allene and alkyne (eq 3).8,12

Addition to Carbonyl Compounds.

Cyclopentanone reacts with allenyllithium to afford a 1:1 mixture of a-allenic and b-alkynic alcohols (eq 4).13 On the other hand, benzophenone gives exclusively homopropargyl alcohol (eq 5).8 Pure allenic acid is obtained by addition to carbon dioxide (eq 6).14

Addition to Epoxides.

Ethylene Oxide reacts with allenyllithium to afford an equal mixture of b-allenic and g-alkynic alcohols (eq 7).15 In the presence of HMPA, 1,3-Butadiene Monoxide reacts with allenyllithium to give b-allenic a-alkenic alcohols (eq 8).5 On the other hand, cyclic vinyl epoxides suffer ring opening by means of the SN2 mechanism in the presence of CuBr.Me2S (see Copper(I) Bromide) (eq 9).

Addition to Amides.

Reaction with N,N-dimethylamides at -78 °C affords pure conjugated allenic ketones (eq 10).4

Substituted Allenyllithiums.

Numerous substituted allenyllithium reagents have been prepared.3b,12 Methylacetylenes with diverse substituents can be metalated at the methyl group to produce 1-substituted allenyllithiums (1) (eq 11), e.g. R = Me,16 n-Pr,17 i-Pr,18 n-Bu,18 t-Bu,18 Et2N,19 PhS,20 R3Si.21 Metalation also works well on propargyl ethers,22 sulfides,22 selenides,23 and amines22 of the type R-C&tbond;C-CH2X. In addition, most mono-, di-, and trisubstituted allenes can be metalated.13 An informative study of regiochemistry in allenyllithium reactions has been carried out using 3,3-dimethylallenyllithium.24

Related Reagents.

Allenylboronic Acid; 1,3-Dilithiopropyne; 3-Lithio-1-triisopropylsilyl-1-propyne; 1-Methoxyallenyllithium; Propargylmagnesium Bromide.

1. Becker, D.; Harel, Z.; Nagler, M.; Gillon, A. JOC 1982, 47, 3297.
2. Psaume, B.; Goré, J. CR(2) 1982, 294, 177 (CA, 1982, 97, 23869g).
3. (a) Roumestant, M. L.; Arseniyadis, S.; Goré, J.; Laurent A. CC 1976, 479. (b) Brandsma, L.; Verkruijisse, H. D. Synthesis of Acetylenes, Allenes and Cumulenes; Elsevier: New York, 1981, p 30.
4. Clinet, J. C.; Linstrumelle, G. NJC 1977, 1, 373.
5. (a) Balme, G.; Doutheau A.; Goré, J.; Malacria, M. S 1979, 508. (b) Doutheau A.; Balme, G.; Malacria, M.; Goré, J. T 1980, 36, 1953.
6. Daniel, P.; Teutsch, J. G.; Costerousse, G.; Deraedt, R. Fr. Patent 2 586 021, 1987 (CA 1988, 108, 6285s).
7. van Dongen, J. P. C. M.; van Dijkman, H. W. D.; de Bie, M. J. A. RTC 1974, 93, 29.
8. Jaffe, F. JOM 1970, 23, 53.
9. Ref. 3b, pp 21-22.
10. Linstrumelle, G.; Michelot, D. CC 1975, 561.
11. Baudouy, R.; Delbecq, F.; Goré, J. TL 1979, 937.
12. The Chemistry of Ketenes, Allenes and Related Compounds, Part I; Moreau, J. L.; Patai, S., Eds.; Wiley: New York, 1980, p 388.
13. Clinet, J. C.; Linstrumelle, G. S 1981, 875.
14. Ref. 3b, p 32.
15. Ref. 3b, p 36.
16. Klein, J; Becker, J. Y. T 1972, 28, 5385.
17. Huynh, C.; Linstrumelle, G. CC 1983, 1133.
18. Suzuki, M.; Morita, Y.; Noyori, R. JOC 1990, 55, 441.
19. Corey, E. J.; Kane, D. E. JOC 1970, 35, 3405.
20. Bridges, A. J.; Thomas, R. D. CC 1983, 485.
21. Hartley, R. C.; Lamothe, S.; Chan, T. H. TL 1993, 34, 1449; Corey, E. J.; Rücker, Ch. TL 1982, 23, 719.
22. Mercier, F.; Epsztein, R.; Holand, S. BSF(2) 1972, 690. Corey, E. J.; Terashima, S. TL 1972, 1815.
23. Reich, H. J.; Shah, S. K.; Gold, P. M.; Olson, R. E. JACS 1981, 103, 3112.
24. Creary, X. JACS 1977, 99, 7632.

Jean-Michel Vatèle

Université Claude-Bernard Lyon 1, Villeurbanne, France

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