Ethyl Lithiopropiolate

(R = Et)

[72036-30-7]  · C5H5LiO2  · Ethyl Lithiopropiolate  · (MW 104.04) (R = Me)

[72036-29-4]  · C4H3LiO2  · Methyl Lithiopropiolate  · (MW 90.01) (R = t-Bu)

[-]  · C7H9LiO2  · t-Butyl Lithiopropiolate  · (MW 132.10) (R = CH2CH=CH2)

[109907-88-2]  · C6H5LiO2  · Allyl Lithiopropiolate  · (MW 116.05)

(used in synthesis of alkynic alcohols by addition to aldehydes, ketones,1 or epoxides2)

Preparative Methods: by treating the alkyl propiolate (e.g. Methyl Propiolate) with n-Butyllithium at low temperature.1 An alternative method uses Lithium Diisopropylamide (LDA).2

Handling, Storage, and Precautions: alkynyllithium reagents are air- and moisture-sensitive. These reagents decompose above -78 °C. The ethyl derivative seems to be slightly more stable than the methyl compound. Ethyl and methyl propiolate should be handled with caution.

Synthesis of Propargyl Alcohols.

The lithium reagent rapidly adds to a variety of aldehydes and ketones to give the alkynic alcohols (eqs 1 and 2).1 These products may be converted into g-butenolides and g-lactones.3 The use of Cerium(III) Chloride provides higher yields in some cases (eq 3).4

Synthesis of Homopropargyl Alcohols.

In the presence of Boron Trifluoride Etherate the reagent will open epoxides to provide homopropargyl alcohols (eq 4).5 Allyl and t-butyl lithiopropiolates have been used in applications where an easily removable protecting group is required.6

Related Reagents.

3,3-Diethoxy-1-propene; Lithium Acetylide; Propynyllithium; 3-Tetrahydropyranyloxy-1-propyne.

1. Midland, M. M.; Tramontano, A.; Cable, J. R. JOC 1980, 45, 28.
2. Herrmann, J. L.; Berger, M. H.; Schessinger, R. H. JACS 1979, 101, 1544.
3. Midland, M. M.; Tramontano, A.; Kazubski A.; Graham, R. S.; Tsai, D. J. S.; Cardin, D. B. T 1984, 40, 1371.
4. Vedejs, E.; Dax, S. L. TL 1989, 30, 2627.
5. Takano, S.; Shimazaki, Y.; Iwabuchi, Y.; Ogasawara, K. TL 1990, 31, 3619.
6. Jungheim, L. N.; Sigmund, S. K. JOC 1987, 52, 4007.

M. Mark Midland

University of California, Riverside, CA, USA

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