Mild and Efficient Tunable Brønsted Acidic Ionic Liquid Catalyzed O-Acetylation and O-Trimethylsilylation with Trimethylsilyl Acetate (TMSOAc) and Hexamethyldisilazane (HMDS)

Abstract

This report discloses a mild and efficient O-acetylation using easily accessible TMSOAc as a novel acetyl reagent and O-trimethylsilylation using HMDS for various alcohols catalyzed by tunable Brønsted acidic ionic liquids (TBAILs). Imidazolium-based TBAILs were prepared by a two-step atom-economic reaction and acidities measured by using UV-visible spectroscopy. Both protections for alcohols were accomplished at room temperature with good to excellent yields, while the products and TBAILs were separated by simple work-up for O-silylation and column chromatography for O-acetylation. Notably, with the simple post-process, TBAILs catalyst in this solvent free method easily recovered and recycled several times without significant degradation.

Expedient method for acylation of amines, alcohols and thiol using trimethylsilyl acetate

“…[5][6][7][8][9][10][11][12] There are several other methods have been reported for acylation of amines, alcohols and thiols which include 4-(Dimethyl amino)pyridine (DMAP) [13][14] , CoCl21 15 , ZnCl2 16 , ZnO 17,18 , CeCl3 19 , ZrOCl2.8H2O 20 , molecular iodine [21][22] , 3-nitrobenzeneboronic acid, 23 La(NO3)3.6H2O, 24 P2O5/Al2O3, 25 NiCl2, 26 Co(II)salen-complex, 27 melamine trisulfonic acid, 28 Sn(TPP)(BF4)2, 29 alkylorthoformate-ZnCl2-Ac2O, 30 vanadium (IV) tetraphenylporphyrin, 31 [Ti IV (salophen)(OTf)2], 32 N-acyl 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) tetraphenylborate salts 33 , iron(III) tosylate, 34 Al(HSO4)3, 35 NbCl5, 36, Zn(Otf)2 37. Recently, metal triflates, other metal salts, [38][39][40][41][42] and ionic liquids etc. [43][44][45][46][47][48] (Scheme 1).…”

A Stoichiometric Solvent-Free Protocol for Acetylation Reactions

“…Such task results particularly relevant for industrial processes ( Sarkar et al, 2016 ). In this respect, acetylation of phenols, alcohols, amines, and thiols has been extensively investigated, with the goal of improving sustainability through homogenous ( Lugemwa et al, 2013 ; Singha and Ray, 2016 ; Temperini et al, 2017 ; Kuciński and Hreczycho, 2018 ; Zhu et al, 2018 ; Jain et al, 2019 ; Chutia and Chetia, 2020 ; Pantawane et al, 2021 ) and heterogenous catalysis ( Rajabi and Luque, 2014 ; Bajracharya and Shrestha, 2018 ; Behera and Patra, 2021 ; Hlatshwayo et al, 2021 ). Indeed, earth-abundant transition metals ( Zhu et al, 2018 ; Jain et al, 2019 ), solvent-free conditions ( Rajabi and Luque, 2014 ; Behera and Patra, 2021 ), and safe acylating reagents ( Singha and Ray, 2016 ; Temperini et al, 2017 ; Pantawane et al, 2021 ) have been employed.…”

“…In this respect, acetylation of phenols, alcohols, amines, and thiols has been extensively investigated, with the goal of improving sustainability through homogenous ( Lugemwa et al, 2013 ; Singha and Ray, 2016 ; Temperini et al, 2017 ; Kuciński and Hreczycho, 2018 ; Zhu et al, 2018 ; Jain et al, 2019 ; Chutia and Chetia, 2020 ; Pantawane et al, 2021 ) and heterogenous catalysis ( Rajabi and Luque, 2014 ; Bajracharya and Shrestha, 2018 ; Behera and Patra, 2021 ; Hlatshwayo et al, 2021 ). Indeed, earth-abundant transition metals ( Zhu et al, 2018 ; Jain et al, 2019 ), solvent-free conditions ( Rajabi and Luque, 2014 ; Behera and Patra, 2021 ), and safe acylating reagents ( Singha and Ray, 2016 ; Temperini et al, 2017 ; Pantawane et al, 2021 ) have been employed. Among transition metal complexes, vanadium covers a chief role as an environment-friendly catalyst for several organic transformations, including oxidation and halogenation reactions ( Conte and Floris, 2010 ; Galloni et al, 2013 ; Floris et al, 2017 ; Coletti et al, 2018 ; Sabuzi et al, 2019 ; Sabuzi et al, 2021 ; Valentini et al, 2021 ).…”