1,3-Dilithiopropyne1

[58335-31-2]  · C3H2Li2  · 1,3-Dilithiopropyne  · (MW 51.93)

(anionic propargyl coupling reagent2,3)

Preparative Methods: from allene via dilithiation;3,4 from propyne via dilithiation;2,5,6 from 1-bromopropyne via polylithiation.7

Handling, Storage, and Precautions: solutions of the reagent are stable at 20 °C and should be handled in the usual way (argon).

Propargylation.

The introduction of a propargylic group as a nucleophile formally requires the protection of the terminal alkyne, e.g. as the trialkylsilylated derivative.8 An efficient alternative is provided by 1,3-dilithiopropyne, readily available via dilithiation of either propyne or Allene.2-6 In particular, the dilithio derivative circumvents the general problem of propargyl and allenyl metal derivatives which equilibrate in solution and often give mixtures of alkenes and alkynes on reaction with electrophiles.9,10

As a rule, 1,3-dilithiopropyne, originating from propyne, reacts preferentially at the 3-position with various electrophiles, including Chlorotrimethylsilane, epoxides, and alkyl halides (eq 1).2,5 Poor regiochemical control has been reported when allyl halides are involved.11 Reaction with carbonyl derivatives leads to the b-alkynyl alcohol (eq 2).12

The reagent also undergoes efficient sequential 1,3-dialkylation. After introduction of the first group at the 3-position, subsequent reaction with a variety of electrophiles (Iodine, Formaldehyde, RX, epoxide) occurs at the terminal alkynic position (eq 3).2,6 Dilithio derivatives of 3-substituted propyne also react preferentially at the propargylic carbon site with electrophiles.5,7,11,13

Controlled lithiation of allene produces an active species which also behaves as a propargyl dianion.14 The presence of hexane was found necessary to obtain pure alkynic derivatives upon alkylation with alkyl halides, including allylic ones (eq 4).3,15 In the presence of N,N,N,N-Tetramethylethylenediamine or in THF, a 1:3 ratio of allenic/alkynic derivatives results.3

The dilithio derivative, obtained from allene at -55 °C with 2 equiv of n-Butyllithium in THF, reacts with the lithium salt of carboxylic acids, leading to conjugated allenyl ketones (eq 5).16,17

The general reactivity of 1,3-dilithiopropyne is in line with the propargylide structure.18 An acetylide structure with a bridging lithium has been calculated for C3H2Li2.19,20

Related Reactions.

High regiocontrol in favor of propargyl products is also shown by the dilithium reagents prepared from phenyl propargyl sulfide11 (eq 6) and selenide.21

Related Reagents.

Allenyllithium; 3-Lithio-1-triisopropylsilyl-1-propyne; 1-Lithio-3-trimethylsilyl-1-propyne; Propynyllithium; Propynylmagnesium Bromide.


1. Fieser, L. F.; Fieser, M. FF 1977, 6, 202; FF 1988, 13, 56.
2. Bhanu, S.; Scheinmann, F. CC 1975, 817.
3. Hooz, J.; Calzada, J. G.; McMaster, D. TL 1985, 26, 271.
4. Hooz, J.; Cabezas, J.; Musmanni, S.; Calzada, J. OS 1990, 69, 120.
5. Hommes, H.; Verkruijsse, H. D.; Brandsma, L. RTC 1980, 99, 113.
6. Bhanu, S.; Scheinmann, F. JCS(P1) 1979, 1218.
7. Bhanu, S.; Khan, E. A.; Scheinmann, F. JCS(P1) 1976, 1609.
8. (a) Corey, E. J.; Kirst, H. A. TL 1968, 5041. (b) Corey, E. J.; Rücker, C. TL 1982, 23, 719.
9. (a) Klein, J. In The Chemistry of the Carbon-Carbon Triple Bond, S. Patai, Ed.; Wiley: New York, 1978; Part 1, Chapter 9. (b) Moreau, J.-L. In The Chemistry of Ketenes, Allenes, and Related Compounds, S. Patai, Ed.; Wiley: New York, (1980); Part 1, Chapter 10. (c) Huntsman, W. D. In Ref. 9b, Part 2, Chapter 15.
10. Suzuki, M.; Morita, Y.; Noyori, R. JOC 1990, 55, 441.
11. Negishi, E.; Rand, C. L.; Jadhav, K. P. JOC 1981, 46, 5041.
12. Mori, K.; Takeuchi, T. T 1988, 44, 333.
13. Pover, K. A.; Scheinmann, F. JCS(P1) 1980, 2338.
14. Jaffe, F. JOM 1970, 23, 53.
15. Bartlett, W. R.; Johnson, W. S.; Plummer, M. S.; Small Jr., V. R. JOC 1990, 55, 2215.
16. Missiaen, P.; De Clercq, P. J. BSB 1990, 99, 271.
17. Cauwberghs, S. C.; De Clercq, P. J. TL 1988, 29, 6501.
18. Priester, W.; West, R.; Chwang, T. L. JACS 1976, 98, 8413.
19. Jemmis, E. D.; Chandrasekhar, J.; von Ragué Schleyer, P. JACS 1979, 101, 2848.
20. Ritchie, J. P.; Bachrach, S. M. JACS 1987, 109, 5909.
21. Reich, H. J.; Shah, S. K.; Gold, P. M.; Olson, R. E. JACS 1981, 103, 3112.

Pierre J. De Clercq & Tom De Geyter

Universiteit Gent, Belgium



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