· (MW 192.23)
(nucleophilic reagent equivalent to an umpoled enone formed from 1,3-dibutoxypropene and t-butyllithium)
Solubility: sol THF/HMPA.
Preparative Method: metalation of 1,3-dibutoxypropene with t-BuLi in THF/HMPA.1
Handling, Storage, and Precautions: sensitive to air, water, and temperature.
A mixture of (E)- and (Z)-1,3-dibutoxypropene is prepared1 from 1,3-dichloro-2-hydroxypropane, through the formation of the known dibutyl ether of glycerol2 and the generation of the final alkene mixture (Z/E = 4:1) through elimination of the tosylate (eq 1). The exclusive formation of the vinyl anion (e.g. 1,3-dibutoxy-1-lithio-1-propene) is observed when the isomeric mixture is treated with t-Butyllithium in THF/HMPA (10:1) at -65 °C (eq 1). Gould and Rossi3 used theoretical calculations to suggest a weakened a-vinyl C-H bond in the (Z)-1,3-dibutoxypropene. Methylated products are observed in the same (Z/E) ratio (i.e. 4:1) as the starting alkenes (eq 1). Other
alkylations with low molecular weight primary bromides or iodides give 70-90% yields of products alkylated at the vinyl position. Other electrophiles such as carbonyls or epoxides were not examined. The overall process corresponds to the generation of a synthetic equivalent of a carbonyl enone synthon (eq 2). This umpoled synthon has been investigated extensively and includes such synthetic equivalents as (1),4 (2),5 and (3).6
This work contrasts with that of Funk (eq 3),7 where the allylic metalation and alkylation of 4H-1,3-dioxin provides a 3-acylvinyl equivalent. Theoretical calculation of bond energies for the 1,3-dioxin system was not performed. Vinyl anions are observed for other cyclic vinyl ethers.8,9 1,3-Hetero allylic systems, e.g. (4)10 and (5),11 containing sulfur also provide the allylic carbanion.
(E)-3-Methylthio-2-propenyl p-Tolyl Sulfone.
- 1. Gould, S. J.; Remillard, B. D. TL 1978, 45, 4353.
- 2. Henze, H. R.; Rogers, B. G. JACS 1939, 61, 433.
- 3. Rossi, H. R.; Gould, S. J.; Remillard, B. D. TL 1978, 4357.
- 4. Tuchinda, P.; Prapansiri, V.; Naengchomnong, V.; Reutrakul, V. CL 1984, 1427.
- 5. Nagao, Y.; Seno, K.; Fujita, E. TL 1979, 34, 3167.
- 6. (a) Gange, D.; Magnus, P. JACS 1978, 100, 7746. (b) Clinet, J. C.; Linstrumelle, G. TL 1978, 1137.
- 7. Review: Biellmann, J. F.; Ducep, J-B. Chemical Reactions; Wiley: New York, 1982; Chapter 1.
- 8. (a) Funk, R. L.; Bolton, G. L. JACS 1988, 110, 1290. (b) Funk, R. L.; Bolton, G. L. TL 1988, 29, 1111.
- 9. Boeckman, R. K.; Bruza, K. J. T 1981, 37, 3997.
- 10. Corey, E. J.; Erickson, B. W.; Noyori, R. JACS 1971, 93, 1724.
- 11. Chen, K.; Sanner, M. A.; Carlson, R. M. SC 1990, 20, 901.
Robert M. Carlson
University of Minnesota, Duluth, MN, USA
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