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Reactions >> Protecting Groups >> Stability

tert-Butyl esters

T. W. Green, P. G. M. Wuts,
Protective Groups in Organic Synthesis,
Wiley-Interscience, New York, 1999, 372-381, 404-408, 728-731.

 

Stability

H2O: pH < 1, 100C pH = 1, RT pH = 4, RT pH = 9, RT pH = 12, RT pH > 12, 100C
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

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.


The hazardous Schmidt procedure for tert-butyl benzoate ester cleavage using NaH in DMF involves BAC2 ester cleavage by NaH-derived NaOH, rather than the proposed E2 elimination of isobutylene by DMF-derived NaNMe2. Powdered KOH in THF is a significantly safer and simpler alternative that effects cleavage of tert-butyl benozoates at ambient temperature in excellent yield.
E. Filali, G. C. Lloyd-Jones, D. A. Sale, Synlett, 2009, 205-208.


E. Filali, G. C. Lloyd-Jones, D. A. Sale, Synlett, 2009, 205-208.


An interesting example of a selective deprotection of tert-butyl esters is reported.
E. Marcantoni, M. Massaccesi, E. Torregiani, G. Bartoli, M. Bosco, L. Sambri, J. Org. Chem, 2001, 66, 4430-4432.