T. W. Green, P. G. M. Wuts,
Protective Groups in Organic Synthesis,
Wiley-Interscience, New York, 1999, 372-381, 404-408, 728-731.
|H2O:||pH < 1, 100°C||pH = 1, RT||pH = 4, RT||pH = 9, RT||pH = 12, RT||pH > 12, 100°C|
|Reduction:||H2 / Ni||H2 / Rh||Zn / HCl||Na / NH3||LiAlH4||NaBH4|
|Oxidation:||KMnO4||OsO4||CrO3 / Py||RCOOOH||I2, Br2, Cl2||MnO2 / CH2Cl2|
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.
Conversion of tert-butyl esters to other functional groups
The reaction of tert-butyl esters with SOCl2 at room temperature provides acid chlorides in very good yields, whereas benzyl, methyl, ethyl, and isopropyl esters are essentially unreactive.
J. A. Greenberg, T. Sammakia, J. Org. Chem., 2017, 82, 3245-3251.