[585-48-8]  · C13H21N  · 2,6-Di-t-butylpyridine  · (MW 191.32)

(weak base and proton scavenger;2-4 prevention of acid-catalyzed side reactions;5-7 vinyl triflate synthesis8,9)

Alternate Names: 2,6-bis(1,1-dimethylethyl)pyridine; BDMEP.

Physical Data: mp 2.2 °C; bp 100-101 °C/23 mmHg; n20D 1.4733; pKa 3.58 (50% EtOH);2 pKa 0.81 (DMSO).3

Solubility: insol H2O; sol alcohol, acetone, and hexane.

Form Supplied in: colorless liquid.

Handling, Storage, and Precautions: potentially toxic; handle with care. Use in a fume hood.

Proton Scavenger.

BDMEP has high basicity in the gas phase,4 but is an abnormally weak base in solution.2,3 The low basicity of BDMEP is due to steric hindrance of solvation.10 Therefore BDMEP forms an HCl salt and compounds with Br2, but does not react with MeI or BF3.2

BDMEP has been used to prevent acid-catalyzed side reactions or nucleophilic reactions by the base in the synthesis of [trans-2,3-trans-5,6-2H4]-1,4-dioxane (eq 1),5 labeled [1-13C]acid chlorides (eq 2),6 steroidal dienes,11 and divinyl ketones. In the last case, Amberlyst/15 pretreated with BDMEP was used (eq 3).7

Catalysis of Enolization and Addition Reactions.

It has been shown that BDMEP and its analogs (e.g. 4-methyl-BDMEP) can be used to prepare vinyl triflates from carbonyl compounds and triflic anhydride.12 Good results were obtained with a polymer-bound BDMEP, which may be easily recycled (eq 4).8 Intermediate vinylsilanes have been obtained from 2,3-dihydro-4H-pyran-4-one derivatives. These have been used in Diels-Alder reactions with alkynes to prepare silyl phenyl ethers (eq 5).9 In the presence of BDMEP, formaldehyde acetals react with trimethylsilyl enol ethers to form b-alkoxy ketones (eq 6).13

Inhibition of Acid-Catalyzed Reactions.

BDMEP was used to eliminate protic acid catalysis in aminium cation-radical initiated Diels-Alder reactions of dienes,14 and vinylcyclopropane-cyclopentene isomerizations.15 Cationic polymerization of isobutene and a-methylstyrene by Ziegler-type catalysts in the presence of BDMEP resulted in a polymer with a higher molecular weight and noticeably narrower molecular weight distribution.16

1. Kanner, B. H 1982, 18, 411.
2. (a) Brown, H. C.; Kanner, B. JACS 1953, 75, 3865. (b) Brown, H. C.; Kanner, B. JACS 1966, 88, 986.
3. Benoit, R. L.; Frechette, M.; Lefebvre, D. CJC 1988, 66, 1159.
4. Arnett, E. M.; Chawla, B. JACS 1979, 101, 7141.
5. Jensen, F. R.; Neese, R. A. JOC 1972, 37, 3037.
6. Luthra, S. K.; Pike, V. W.; Brady, F. Appl. Radiat. Isot. 1990, 41, 471.
7. Nakamura, E.; Kubota, K.; Isaka, M. JOC 1992, 57, 5809.
8. (a) Wright, M. E.; Pulley, S. R. JOC 1987, 52, 1623, 5036. (b) Wright, M. E.; Pulley, S. R. JOC 1989, 54, 2886.
9. Obrecht, D. HCA 1991, 74, 27.
10. (a) McDaniel, D. H.; &OOuml;zcan, M. JOC 1968, 33, 1922. (b) Bernasconi, C. F.; Carre, D. J. JACS 1979, 101, 2707.
11. Prelle, A.; Winterfeldt, E. H 1989, 28, 333.
12. Stang, P. J.; Treptow, W. S 1980, 283.
13. Murata, S.; Suzuki, M.; Noyori, R. T 1988, 44, 4259.
14. (a) Gassman, P. G.; Singleton, D. A. JACS 1984, 106, 7993. (b) Reynolds, D. W.; Lorenz, K. T.; Chiou, H.-S.; Bellville, D. J.; Pabon, R. A.; Bauld, N. L. JACS 1987, 109, 4960. (c) Schmittel, M.; Seggern, H. v. AG(E) 1991, 30, 999.
15. Dinnocenzo, J. P.; Conlon, D. A. JACS 1988, 110, 2324.
16. Kennedy, J. P. J. Macromol. Sci., Chem. 1982, A18, 3.

Rafael R. Kostikov

St. Petersburg State University, Russia

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