Surprisingly, only a 0.05−2 mol % of DMAP can efficiently promote acylation of alcohols with acid anhydrides under auxiliary base- and solvent-free conditions to give the corresponding esters in high yields. Furthermore, the recovery and reuse of commercially available polystyrene-supported DMAP was achieved without using any solvents.
A. Sakakura, K. Kawajiri, T. Ohkubo, Y. Kosugi, K. Ishihara, J. Am. Chem. Soc., 2007, 129, 14775-14779.
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.
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.
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, phenols, amines and thiols may easily be converted into acetate derivatives by treatment with acetic anhydride in the presence of acetonyltriphenylphosphonium bromide in good yields at room temperature. With the same precatalyst, both aliphatic and aromatic aldehydes can be transformed into the corresponding gem-diacetates under reflux conditions.
A. T. Khan, L. H. Choudry, S. Ghosh, Eur. J. Org. Chem., 2005, 2782-2787.
The data of a study on mixed aliphatic-aromatic anhydrides suggest that during the Yamaguchi esterification reaction, a symmetric aliphatic anhydride is produced in situ, which upon reaction with an alcohol yields the ester. A one-pot procedure for the regioselective synthesis of aliphatic esters is described using benzoyl or p-toluoyl chloride instead of the sterically hindered Yamaguchi acid chloride.
I. Dhimitruka, J. SantaLucia, Org. Lett., 2006, 8, 47-50.
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.
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.
A convenient procedure allows the synthesis of esters and thioesters from the corresponding carboxylic acid using TFFH as the coupling reagent. The preparation of N-acyl-dithiocarbamates from carboxylic acids and 1,3-thiazolidine-2-thione is also described.
M. Pittelkow, F. S. Kamounah, U. Boas, B. Pedersen, J. B. Christensen, Synthesis, 2004, 2485-2492.
Er(OTf)3 is an efficient Lewis acid catalyst in a mild deprotection of benzylidene derivatives. A simultaneous cleavage of benzylidene acetals and peracetylation of the substrates is obtained in quantitative yields in acetic anhydride as solvent.
A. Procopio, R. Dalpozzo, A. De Nino, L. Maiuolo, M. Nardi, G. Romeo, Org. Biomol. Chem., 2005, 3, 4129-4133.
In a simple protocol for the synthesis of α-diarylacetic esters from benzoins, in situ generated acetals assist rapid 1,2-aryl migration in a stereospecific manner, paving the way to make enantioenriched α-diarylacetic esters from easily accessible enantiopure benzoins.
R. B. Kothapalli, R. Niddana, R. Balmurugan, Org. Lett., 2014, 16, 1278-1281.
Stereodefined enol derivatives of aldehydes are prepared from terminal alkynes through Cp2ZrCl2-catalyzed methylalumination and subsequent oxygenation with peroxyzinc species and electrophilic trapping with carboxylic anydrides. The tandem carbometalation/oxygenation tolerates free and protected alcohols, heterocycles, olefins, and nitriles.
J. R. DeBergh, K. M. Spivey, J. M. Ready, J. Am. Chem. Soc., 2008, 130, 7828-7829.