t-Butoxyacetylene

[89489-28-1]  · C6H10O  · t-Butoxyacetylene  · (MW 98.16)

(thermal and CuI-catalyzed dimerization;1 synthesis of silylketenes;2 synthesis of macrocyclic lactones via ketene intermediates3)

Physical Data: bp ca. 23 °C/22 mmHg.

Solubility: sol organic solvents.

Form Supplied in: pale yellow liquid.

Analysis of Reagent Purity: 1H NMR, 13C NMR, IR, and gas chromatography.

Preparative Methods: bromination of ethyl vinyl ether and displacement by t-butanol provides a mixed acetal (eq 1); substitution of ethoxy by chloride and dehydrochlorination then gives rise to b-bromovinyl ether (eq 2), which upon dehydrobromination with base generates t-butoxyacetylene (eq 3).4 The overall yield from ethyl vinyl ether is 34%. This substance has also been prepared by bromination of t-butoxy vinyl ether followed by stepwise elimination of HBr.5 The preparation of t-butoxyacetylene from an appropriate 1-chloro-1-fluoroalkene has also been reported.6

Purification: distillation at 23 °C/0.5 mmHg, collecting material at -78 °C, followed by redistillation at 23 °C/22 mmHg, collecting at 0 °C.

Handling, Storage, and Precautions: t-butoxyacetylene should be used as distilled for best results (clear liquid). It turns pale yellow upon storage at -10 °C (freezer) and is stable for a few months under these conditions.

Dimerization.

The CuI-catalyzed oxidative dimerization of t-butoxyacetylene under modified Hay conditions has been found to proceed smoothly (eq 4).1a The resulting 1,4-di-t-butoxy-1,3-butadiyne is interesting with respect to its polymerization properties. The controlled polymerization of t-butoxyacetylene via tungstacarbene compounds has been reported.7 Thermal dimerization of t-butoxyacetylene under mild conditions, so that the generated low concentration of the parent ketene prevents its oligomerization, provides 3-t-butoxycyclobutenone in good yield (eq 5) which in turn can be hydrolyzed to 1,3-cyclobutanedione.1b

Synthesis of Silylketenes.

The C-silylation of t-butoxyacetylene has been achieved by deprotonation and subsequent silylation (eq 6).2 Thermally induced elimination of isobutylene from these derivatives via a retro-ene type rearrangement delivers silylketenes at much lower temperature than from the corresponding ethoxyacetylene compounds (eq 7).8 In the case of 1-t-butoxy-2-(trimethylsilyl)acetylene, thermolysis at 50-55 °C in the presence of diphenylamine provided N,N-diphenyl(trimethylsilyl)acetamide in high yield (eq 8).2 The C-alkylation of t-butoxyacetylene can be carried out in a similar manner.3a,4

Macrocyclic Lactones.

Addition of substituted t-butoxyacetylene derivatives to refluxing MeCN and Triethylamine under high-dilution conditions produces macrocyclic lactones in 57% yield via a ketene intermediate (e.g. eq 9).3a Similar lactonizations are shown in eqs 10 and 11. As indicated, the cross-coupling of t-butoxyacetylene with conjugated enynes (eq 10) is more efficient than that with simple alkynes (eq 11).3b


1. (a) Valentí, E.; Pericàs, M. A.; Serratosa, F. JACS 1990, 112, 7405. (b) Pericàs, M. A.; Serratosa, F.; Valentí, E. S 1985, 1118.
2. Valentí, E.; Pericàs, M. A.; Serratosa, F. JOC 1990, 55, 395.
3. (a) Funk, R. L.; Abelman, M. M.; Jellison, K. M. SL 1989, 36. (b) Magriotis, P. A.; Vourloumis, D.; Scott, M. E.; Tarli, A. TL 1993, 34, 2071.
4. Pericàs, M. A.; Serratosa, F.; Valentí, E. T 1987, 43, 2311.
5. (a) Van Daalen, J. J.; Kraak, A.; Arens, J. F. RTC 1961, 80, 810. (b) Potman, R. P.; Janssen, N. J. M. L.; Scheeren, J. W.; Nivard, R. J. F. JOC 1984, 49, 3628.
6. Viehe, H. G. AG 1963, 75, 638.
7. Parlier, A.; Rudler, H.; Platzer, N.; Fontanille, M.; Soum, A. JCS(D) 1987, 1041.
8. (a) Brandsma, L.; Bos, H. J. T.; Arens, J. F. Chemistry of Acetylenes; Viehe, H. G., Ed.; Dekker: New York, 1969; pp 808-810. (b) Moyano, A.; Pericàs, M. A.; Serratosa, F.; Valentí, E. JOC 1987, 52, 5532. (c) Ruden, R. A. JOC 1974, 39, 3607.

Plato A. Magriotis

West Virginia University, Morgantown, WV, USA



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