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Reactions >> Protecting Groups >> Stability

Acetic acid esters

Ac-OR, Acetic acid esters, Acetate esters, Acetates

T. W. Green, P. G. M. Wuts, Protective Groups in Organic Synthesis,
Wiley-Interscience, New York, 1999, 150-160, 712-715.

 

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

Protection


Phosphomolybdic acid (PMA) is a simple and efficient catalyst for the acetylation of structurally diverse alcohols, phenols, and amines. Acetylation reactions with acetic anhydride proceed in excellent yield in the presence of a catalytic amount of PMA at ambient temperature within a relatively short reaction time under solvent-free conditions.
S. T. Kadam, S. S. Kim, Synthesis, 2008, 267-268.


Acylation of alcohols, thiols, and sugars were studied with a variety of Lewis acids, and it was found that Cu(OTf)2 was very efficient in catalyzing the reaction under mild conditions in CH2Cl2.
K. L. Chandra, P. Saravan, R. K. Singh, V. K. Singh, Tetrahedron, 2002, 58, 1369-1374.


Copper(II) tetrafluoroborate efficiently catalyzes acetylation of structurally diverse phenols, alcohols, thiols, and amines with stoichiometric amounts of Ac2O under solvent-free conditions at room temperature. Acid-sensitive alcohols are smoothly acetylated without competitive side reactions.
A. K. Chakraborti, R. Gulhane, Shivani, Synthesis, 2004, 111-115.


Various alcohols, thiols, phenols, and amines can be acetylated using acetic anhydride in the presence of catalytic quantity of silver triflate. The method proceeds under mild conditions, does not involve cumbersome workup, and the resulting products are obtained in high yields within a reasonable time.
R. Das, D. Chakraborty, Synthesis, 2011, 1621-1625.


Molecular iodine catalyzes acetalation and acetylation of sugars with stoichiometric amounts of enol acetates under solvent-free conditions to give orthogonally protected sugar derivatives in short time and good yields. At lower temperature, it is possible to obtain the acetonide acetate as a single product whereas peracetate is the major product at higher temperature.
D. Mukherjee, B. A. Shah, P. Gupta, S. C. Taneja, J. Org. Chem., 2007, 72, 8965-8969.


Other Syntheses of Acetic Acid Esters


A counterattack protocol for differential acetylative cleavage of phenylmethyl ether allows the reuse of the phenylmethyl moiety as benzyl bromide, thus providing advantages in terms of waste minimization and atom economy. The applicability of this methodology has been extended for solid phase organic reactions with the feasibility of reuse of the solid support.
A. K. Chakraborti, S. V. Chankeshwara, J. Org. Chem., 2009, 74, 1367-1370.


Deprotection


N,N-diarylammonium pyrosulfate efficiently catalyzes the hydrolysis of esters under organic solvent-free conditions. This reverse micelle-type method is successfully applied to the hydrolysis of various esters without the decomposition of base-sensitive moieties and without any loss of optical purity for α-heterosubstituted carboxylic acids.
Y. Koshikari, A. Sakakura, K. Ishihara, Org. Lett., 2012, 14, 3194-3197.


Acetyl-, benzoyl- and pivoyl-protected alcohols and phenols undergo smooth deacylation in a two-phase system of powdered NaOH and Bu4NHSO4 in THF or CH2Cl2.
R. D. Crouch, J. S. Burger, K. A. Zietek, A. B. Cadwallader, J. E. Bedison, M. M. Smielewska, Synlett, 2003, 991-992.