Ultrasound promoted acetylation of alcohols in room temperature ionic liquid under ambient conditions

Abstract

The O-acetylation of alcohols with acetic anhydride to the corresponding esters has been achieved in excellent isolated yields in short reaction time at ambient conditions under ultrasonic irradiation in the absence of any added catalyst using a room temperature ionic liquid as the medium as well as a promoter for the reaction. The products could be isolated by distillation or selective extraction from the non-volatile ionic liquid, which could be recycled giving rise to a process with minimal waste.

Ionic Liquids as Carbene Catalyst Precursors in the One-Pot Four-Component Assembly of Oxo Triphenylhexanoates (OTHOs)

“…Moreover, ILs themselves can also be used as catalysts [7,8]. This has been exemplified in several syntheses of heterocycles [9], cycloadditions [10], and acetylations of alcohols [11,12]. Rate enhancements seen in these reactions have been attributed to a range of activation modes such as hydrogen bonding [10,13], and Lewis acid [11] and base [12] catalysis.…”

“…This has been exemplified in several syntheses of heterocycles [9], cycloadditions [10], and acetylations of alcohols [11,12]. Rate enhancements seen in these reactions have been attributed to a range of activation modes such as hydrogen bonding [10,13], and Lewis acid [11] and base [12] catalysis. Other activation strategies can be invoked by deprotonation of dialkyl imidazolium-based ILs with a base, thus generating an N-heterocyclic carbene (NHC) (Figure 1a).…”

Highly efficient conversion of aromatic acylals to 3, 4-dihydropyrimidinones: a new protocol for the Biginelli reaction

“…10 However, it suffers from low yields (20-50%) of products. Therefore, several improved methodologies mainly using Lewis acids, 11,12 triflates, 13 microwave-assisted methodologies 14 and ultrasonic mediated methods 15 have been reported in the literature. However, in spite of their potential utility many of the existing methods suffers from the drawbacks such as the use of strong acidic conditions, longer reaction times, tedious workup, environmental disposal problems and lower yields of the products, leaving scope for further development of an efficient and versatile method for Biginelli reaction.…”

Efficient and Rapid Solvent-Free Acetylation of Alcohols, Phenols, and Thiols Using Catalytic Amounts of Sodium Acetate Trihydrate

“…Acetylation of alcohols is traditionally carried out in the presence of excessive amounts of acetic anhydride or acetyl chloride and an amine base [10]. More efficient alternative methods are developed in recent years using Lewis acids [11][12][13][14][15][16], solid supports [17][18][19][20][21][22][23], microwave irradiation [24][25][26], ultrasonic activation [27], solid protic acids [28][29][30], ionic liquids [31][32][33], and enzymes [34,35]. However, still in many of these methods use of excessive acetic anhydride, application of toxic metal containing catalysts, and involvement of tedious work-up conditions are required.…”