tert-Butyl ethers
T. W. Green, P. G. M. Wuts,
Protective Groups in Organic
Synthesis,
Wiley-Interscience, New York, 1999, 65-67, 708-711.
Stability
H2O: | pH < 1, 100°C | pH = 1, RT | pH = 4, RT | pH = 9, RT | pH = 12, RT | pH > 12, 100°C |
Bases: | LDA | NEt3, Py | t-BuOK | Others: | DCC | SOCl2 |
Nucleophiles: | RLi | RMgX | RCuLi | Enolates | NH3, RNH2 | NaOCH3 |
Electrophiles: | RCOCl | RCHO | CH3I | Others: | :CCl2 | Bu3SnH |
Reduction: | H2 / Ni | H2 / Rh | Zn / HCl | Na / NH3 | LiAlH4 | NaBH4 |
Oxidation: | KMnO4 | OsO4 | CrO3 / Py | RCOOOH | I2, Br2, Cl2 | MnO2 / CH2Cl2 |
Protection
An eco-compatible method for the formation of tert-butyl ethers of
alcohols and phenols is performed in solvent-free conditions at room temperature
using catalytic amount of Er(OTf)3. The catalyst is easily recovered
and reused several times without loss of activity. In addition, the tert-butyl
group is removed very quickly from alcohols and phenols in methanol in the
presence of Er(OTf)3 using MW irradiation.
A. Procopio, P. Costanzo, M. Curini, M. Nardi, M. Oliverio, R. Paonessa, Synthesis, 2011,
73-78.
A mild reaction for the protection of alcohols as t-butyl
ethers proceeds with Mg(ClO4)2 and Boc2O and
shows general applicability. In addition, preliminary results indicate that the
CeCl3·7H2O/NaI system is a very suitable catalyst for the
deprotection of t-butyl ethers.
G. Bartoli, M. Bosco, M. Locatelli, E. Marcantoni, P. Melchiorre, L. Sambri,
Org. Lett., 2005,
7, 427-430.
Treatment of various free amino acids with 1.1 equivalents of
bis(trifluoromethanesulfonyl)imide in tert-butyl acetate directly
afforded tert-butyl esters with free amino groups quickly and in good
yields. In addition, various carboxylic acids and alcohols without amino groups
were converted into tert-butyl esters and ethers, respectively, in high
yields in the presence of catalytic amounts of Tf2NH.
C. Ogasa, K. Kayano, K. Namba, Synlett, 2024,
35,
235-239.
A noncoordinating acid-base catalyst [bis(trifluoromethane)sulfonimide and
2,6-lutidine] mediates a mild and nonreversible tert-butylation of
alcohols and phenols with tert-butyl 2,2,2-trichloroacetimidate as a
tert-butylation reagent. This method allows the use of substrates containing
acid sensitive groups such as ketal, Boc, and boronate esters.
K. R. Fandrick, N. D. Patel, S. Radomkit, A. Chatterjee, S. Braith, D. R.
Fandrick, C. A. Busacca, C. H. Senanayake, J. Org. Chem., 2021, 86,
4877-4882.
Deprotection
Aqueous phosphoric acid is an effective, environmentally benign, selective
and mild reagent for the deprotection of tert-butyl carbamates, tert-butyl
esters, and tert-butyl ethers. CBZ carbamates, azetidine, benzyl and
methyl esters, TBDMS, and methyl phenyl ethers are tolerated. The reactions are
high yielding, and the workup is convenient.
B. Li, M. Berliner, R. Buzon, C. K.-F. Chiu, S. T. Colgan, T. Kaneko, N.
Keene, W. Kissel, T. Le, K. R. Leeman, B. Marquez, R. Morris, L. Newell, S.
Wunderwald, M. Witt, J. Weaver, Z. Zhang, Z. Zhang, J. Org. Chem., 2006,
71, 9045-9050.
A mild reaction for the protection of alcohols as t-butyl
ethers proceeds with Mg(ClO4)2 and Boc2O and
shows general applicability. In addition, preliminary results indicate that the
CeCl3·7H2O/NaI system is a very suitable catalyst for the
deprotection of t-butyl ethers.
G. Bartoli, M. Bosco, M. Locatelli, E. Marcantoni, P. Melchiorre, L. Sambri,
Org. Lett., 2005,
7, 427-430.
The combination of the tris-4-bromophenylamminium radical cation, commonly
known as magic blue (MB•+), and triethylsilane mediates a mild OtBu
deprotection. Magic blue catalytically facilitates the cleavage of the C-O bond
in tert-butyl carbamates, carbonates, esters, and ethers in a high
isolated yield under mild conditions, and sacrificial triethylsilane accelerates
the reaction.
D. Hidasová, Tomáš Slanina, J. Org. Chem., 2023, 88,
6932-6938.
A. Procopio, P. Costanzo, M. Curini, M. Nardi, M. Oliverio, R. Paonessa, Synthesis, 2011,
73-78.
Other Syntheses of t-Butyl-protected Hydroxyl Groups
A palladium-catalyzed synthesis of aryl tert-butyl ethers from a variety
of unactivated aryl bromides or chlorides is described. The ether products,
which are precursors to phenols, are obtained in very good yield in the presence
of air-stable dialkylphosphinobiphenyl ligands.
C. A. Parrish, S. L. Buchwald, J. Org. Chem., 2001,
66, 2498-2500.
A practical and environmentally friendly oxidation of aryl olefins to
arylethanone derivatives by using a Cu(I) catalyst and tert-butyl
hydroperoxide (TBHP) provides 2-tert-butoxy-1-arylethanones in good
yields under mild conditions with high selectivity. In this method, TBHP acts
not only as an oxidant but also as the tert-butoxy and carbonyl oxygen
sources.
J. Zhang, D. Xiao, H. Tan, W. Liu, J. Org. Chem., 2020, 85,
3929-3935.