[67965-43-9]  · C6H11LiSi  · 1-Lithio-3-trimethylsilyl-1-propyne  · (MW 118.20)

(powerful nucleophilic source of 3-trimethylsilylpropynyl unit for many electrophiles)

Solubility: sol THF, toluene.

Preparative Methods: prepared in situ under nitrogen by reaction of commercially available propargyltrimethylsilane1 with n-Butyllithium in THF at -78 °C2 or by reaction of 3,3-dichloroallyltrimethylsilane and n-BuLi in THF at -90 °C.3

Handling, Storage, and Precautions: must be prepared and transferred under inert gas (Ar or N2) to exclude oxygen and moisture; stable at room temperature.

Additions to Carbonyl Compounds.

Paraformaldehyde reacts with 1-lithio-3-trimethylsilyl-1-propyne (1) at room temperature to give the hydroxymethylated product. Oxidation gave the alkynic aldehyde, which served as a synthetic equivalent for the butadienyl carbenium ion.4 Reduction with Lithium Aluminum Hydride gave the allylic alcohol which was used to protect carboxylic acids as esters which could be deprotected under mild palladium-catalyzed conditions (eq 1).5 Secondary and tertiary alcohols were prepared for hydrostannylation studies by addition of (1) to a range of aldehydes and ketones (eq 2).2 1,4-Benzoquinones were prepared by thermolysis in refluxing xylene of the adducts of cyclobutenediones and (1) (eq 3).6 Addition to ethyl acetate, in the presence of Boron Trifluoride Etherate, provided the alkynic ketone in superior yield to addition to acetaldehyde and oxidation, due to the low yield in the latter step (eq 4).7

Alkylations of Alkyl Halides.

Methylation of (1) with Iodomethane in THF/HMPA required extended time at reflux (eq 5).2 Alkylation of THP-protected linear iodo alcohols was achieved in modest yield at rt in the same solvent system (eq 6).8 (Iodomethyl)trimethylsilane reacted well in refluxing THF alone to give 1,4-bis(trimethylsilyl)-2-butyne.9

Additions to Epoxides.

1-Lithio-3-trimethylsilyl-1-propyne reacts well with epoxides only in the presence of Lewis acids. Diethylaluminum Chloride in toluene was used to promote addition to Ethylene Oxide10 (eq 7) while boron trifluoride etherate in THF at low temperature ensured high regioselectivity in additions to monosubstituted epoxides (eq 8).11

Reactions with Other Electrophiles.

n-Butyllithium deprotonates the vinyl proton of 3,3-dichloroallyltrimethylsilane in THF, which leads to elimination of lithium chloride, and subsequent metal-halogen exchange produces 1-lithio-3-trimethylsilyl-1-propyne in situ (eq 9). If excess n-butyllithium is present, further metalation occurs to give a dilithium species as confirmed by addition of Chlorotrimethylsilane (eq 10).3 1,3-Bis(trimethylsilyl)-1-propyne may be obtained by metalation of propargyltrimethylsilane with butyllithium and reaction with chlorotrimethylsilane (eq 11).12 Lithium 3-trimethylsilyl-1-propynyltributylborate, formed by addition of 1-lithio-3-trimethylsilyl-1-propyne to Tri-n-butylborane, reacted with Trimethylsilylmethyl Trifluoromethanesulfonate followed by protonolysis to give the bisallylsilane (eq 12).13

Related Reagents.

3-Chloro-1-propynyllithium; Lithium (Trimethylsilyl)acetylide; Propynyllithium.

1. Slutsky, J.; Kwart, H. JACS 1973, 95, 8678.
2. Nativi, C.; Taddei, M. JOC 1988, 53, 820.
3. Seyferth, D.; Mammarella, R. E. JOM 1978, 156, 299.
4. Angoh, A. G.; Clive, D. L. J. CC 1984, 534.
5. Mastalerz, H. JOC 1984, 49, 4092.
6. Karabelas, K.; Moore, H. W. JACS 1990, 112, 5372.
7. Nativi, C.; Taddei, M.; Mann, A. T 1989, 45, 1131.
8. Schinzer, D.; Allagiannis, C.; Wichmann, S. T 1988, 44, 3851.
9. Pornet, J. JOM 1988, 340, 273.
10. Hiemstra, H.; Sno, M. H. A. M.; Vijn, R. J.; Speckamp, W. N. JOC 1985, 50, 4014.
11. Mohr, P. TL 1992, 33, 2455.
12. Pornet, J.; Mesnard, D.; Miginiac, L. TL 1982, 23, 4083.
13. Wang, K. K.; Yang, K. E. TL 1987, 28, 1003.

Nicholas Greeves

University of Liverpool, UK

Copyright 1995-2000 by John Wiley & Sons, Ltd. All rights reserved.