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Reactions >> Protecting Groups >> Stability

Benzoic acid esters

Bz-OR, Benzoate ester, Benzoate

T. W. Green, P. G. M. Wuts,
Protective Groups in Organic Synthesis,
Wiley-Interscience, New York, 1999, 173-178, 712-715.

 

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


4-(N,N-Dimethylamino)pyridine hydrochloride (DMAP·HCl) was used as a recyclable catalyst for the acylation of inert alcohols and phenols under base-free conditions. The catalyst can be reused more than eight times without loss in activity and works with various acylating reagents.
Z. Liu, Y. Liu, Q. Wang, Org. Lett., 2014, 16, 236-239.


A very fast acylation of alcohols with benzoyl chloride in the presence of TMEDA at -78°C afforded the corresponding benzoates in excellent yields.
T. Sano, Synthesis, 1999, 1141-1144.


Carbonylimidazole derivatives are highly active acylation reagents for esterification and amidation in the presence of pyridinium salts as catalysts. These reactions are thought to involve both Brønsted acid and nucleophilic catalysis. This mode of activation has been applied to the synthesis of difficult to access oxazolidinones, as well as esters and amides.
S. T. Heller, T. Fu, R. Sarpong, Org. Lett., 2012, 14, 1970-1973.


The use of diacyl disulfide as an acylation reagent enables an efficient ester formation under DMAP catalysis. A site-selective acylation of phenolic and primary aliphatic hydroxyl groups greatly expands the scope of protecting group chemistry. Diacyl disulfides offer excellent moisture tolerance, high efficiency, and potential in synthetic chemistry and biologically meaningful natural product modification.
H.-X. Liu, Y.-Q. Dang, Y.-F. Yuan, Z.-F. Xu, S.-X. Qiu, H.-B. Tan, Org. Lett., 2016, 18, 5584-5587.


Reversible covalent interactions of organoboron compounds enable a regioselective borinic acid-catalyzed acylation of polyols. This catalytic protocol enables differentiation of the secondary OH groups of a wide range of carbohydrate derivatives with diverse acid chloride and chloroformate reagents, using a structurally simple diarylborinic acid-derived catalyst.
D. Lee, M. S. Taylor, J. Am. Chem. Soc., 2011, 133, 3724-3727.


Highly regioselective monoprotection of hydroxyl groups in sugars was accomplished along with high chemical yield in the presence of dimethyltin dichloride as catalyst. The regioselectivity of the benzoylation of sugars is based on a stereorelationship among their hydroxyl groups.
Y. Demizu, Y. Kubo, H. Miyosho, T. Maki, Y. Matusumura, N. Moriyama, O. Onomura, Org. Lett., 2008, 10, 5075-5077.


Other Syntheses of Benzoate-protected Hydroxyl Groups


A very efficient and highly regioselective ring-opening reaction of epoxides with benzoic acid and its derivatives in the presence of cat. amount of tetrabutylammonium bromide (TBAB) in anhydrous acetonitrile gave selectively protected diols.
A. Khalafi-Nezhad, M. N. Soltani Rad, A. Khoshnood, Synthesis, 2003, 2552-2558.


Deprotection


Acyloxymethyl radicals, that add to imines, were generated from the corresponding iodomethyl esters by the action of dimethylzinc or triethylborane. A facile hydrolysis of the acyloxy moiety of the adducts gave the corresponding amino alcohols in good yield.
K.-i. Yamada, M. Nakano, M. Maekawa, T. Akindele, K. Tomioka, Org. Lett., 2008, 10, 3805-3808.


The reaction of different esters, thioesters and amides derived from pivalic, benzoic and 4-tert-butylbenzoic acids with an excess of lithium and a catalytic amount of naphthalene led, after methanolysis, to the corresponding alcohols, thiols and amines, respectively, through a reductive non-hydrolytic procedure.
C. Behloul, D. Guijarro, M. Yus, Synthesis, 2006, 309-314.