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.
The reaction between carboxylic acids and dialkyl dicarbonates, in the presence of a weak Lewis acid such as magnesium chloride and the corresponding alcohol as the solvent, leads to esters in excellent yields. The mechanism involves a double addition of the acid to the dicarbonate, affording a carboxylic anhydride and CO2.
G. Bartoli, M. Bosco, A. Carlone, R. Dalpozzo, E. Marcantoni, P. Melchiorre, L. Sambri, Synthesis, 2007, 3489-3496.
The coupling reagent ethyl 2-cyano-2-(2-nitrobenzenesulfonyloxyimino)acetate (o-NosylOXY) produces only byproducts that can be easily recovered and reused for the synthesis of the same reagent, making coupling reactions to yield amides, hydroxamates, peptides, and esters more environmentally friendly and cost-effective.
D. Dev, N. B. Palakurthy, K. Thalluri, J. Chandra, B. Mandal, J. Org. Chem., 2014, 79, 5420-5431.
A macroporous polymeric acid catalyst enables a direct esterification of carboxylic acids and alcohols at 50 to 80°C without removal of water to give the corresponding esters with high yield. Flow esterification for the synthesis of biodiesel fuel was also achieved by using a column-packed macroporous acid catalyst under mild conditions.
M. Minakawa, H. Baek, Y. M. A. Yamada, J. W. Han, Y. Uozumi, Org. Lett., 2013, 15, 5798-5801.
Borane-tetrahydrofuran complex or borane-methyl sulfide complex is used to generate triacyloxyboranes, which can be effectively reacted with various nucleophiles (alkylamines, arylamines, hydrazides, alcohols, phenols) at reflux in toluene to provide the corresponding amides and esters in excellent yield.
Z. Huang, J. R. Reilly, R. N. Buckle, Synlett, 2007, 1026-1030.
Protic Acid Immobilized on Solid Support as an Extremely Efficient Recyclable Catalyst System for a Direct and Atom Economical Esterification of Carboxylic Acids with Alcohols
A. K. Chakraborti, B. Singh, S. V. Chankeshwara, A. R. Patel, J. Org. Chem., 2009, 74, 5967-5974.
Silica chloride is an efficient catalyst for esterification of carboxylic acids with alcohols as well as for transesterification of esters by both alcoholysis and acidolysis.
K. V. N. S. Srinivas, I. Mahender, B. Das, Synthesis, 2003, 2479-2482.
An oxyma derivative, (2,2-dimethyl-1,3-dioxolan-4-yl)methyl 2-cyano-2-(hydroxyimino)acetate, displayed a remarkable effect on selective esterifications of primary alcohols. A wide range of carboxylic acids could be esterified with primary alcohols by using EDCI, NaHCO3 in 5% H2O-CH3CN. The Oxyma derivative can be removed after the reaction via a simple basic or an acidic aqueous workup procedure.
Y. Wang, B. A. Aleiwi, Q. Wang, M. Kurosu, Org. Lett., 2012, 14, 4910-4913.
Carboxylic acid esters can be prepared in very good yields at room temperature from an acid and either a phenol or an aliphatic alcohol using the peptide coupling reagents TBTU, TATU, or COMU, in the presence of organic bases. Reactions using TBTU and TATU are faster but do not occur with tertiary alcohols. Selective monoesterifications of diols and polyols can be achieved with choice of base and coupling agent.
J. K. Twibanire, T. B. Grindley, Org. Lett., 2011, 13, 2988-2991.
Imidazole carbamates and ureas are chemoselective esterification and amidation reagents. A simple synthetic procedure allows the conversion of a wide variety of carboxylic acids to ester or amide analogues in high yields.
S. T. Heller, R. Sarpong, Org. Lett., 2010, 12, 4572-4575.
Cobalt(II) chloride hexahydrate efficiently catalyzes the acetylation of alcohols with AcOH in high yields without the need to remove water. This protocol is also effective with other carboxylic acids. The catalyst can be recycled.
S. Velusamy, S. Borpuzari, T. Punniyamurthy, Tetrahedron, 2005, 61, 2011-2015.
A new facile method for selective monoesterification of diols - in particular oligoethylene glycols - has been developed. The reaction of diols with aromatic and aliphatic acids in presence of Al2O3 and MeSO3H gave monoesterified products in excellent yields without use of any solvents.
H. Sharghi, M. Hosseini Sarvari, Tetrahedron, 2003, 59, 3627-3633.
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.
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.