A green protocol for chemoselective O-acylation in the presence of zinc oxide as a heterogeneous, reusable and eco-friendly catalyst

Air-stable titanocene bis(perfluorooctanesulfonate) as a new catalyst for acylation of alcohols, phenols, thiols, and amines under solvent-free condition

“…TMSOTf [32] and Cp 2 Ti(OTf) 2 [40] show high catalytic activity but they are known to be unstable in air (Table 5, Entries 3,4). The reference catalysts of Sc(OTf) 3 [30], Bi(OTf) 3 [33], Mg(NTf 2 ) 2 [23], I 2 [38] and DMAP [5] (highly toxic; e.g., intravenous LD50 in the rat: 56 mg/ kg) [23], and AgOSO 2 C 8 F 17 [43], show lower catalytic activity than Cp 2 Ti(OSO 2 C 8 F 17 ) 2 (Table 5, Entries 5-9). Furthermore, these catalysts are hydrolytic in air and liberate CF 3 SO 3 H which has been considered as powerful catalyst by Hollis et al [42].…”

“…Besides being environmentally friendly, solvent-free reactions in many cases can offer synthetic advantages in terms of yield, selectivity and simplicity of reaction procedure. The use of solvent-free acetylation procedure is limited [21][22][23][24][25][26][27][28][29][35][36][37][38].…”

ZnO NPs: an efficient and reusable nanocatalyst for the synthesis of nitrones from DAG using H2O as a solvent at room-temperature

“…This catalyst has been widely used in organic reactions, but it has not been carefully studied as a catalyst for the synthesis of nitrone derivatives from DAG in water as a solvent until now [38]. Adsorption of the starting materials on the ZnO surface with the coordination of accessible zinc cations to functional groups led to the activation of substrates which enhanced the reactions rates and yields [39][40][41][42]. Due to the importance of nitrone compounds, the discovery and introduction of mild, economic and faster conditions using new catalytic methods are required.…”

Zinc dust: An extremely active and reusable catalyst in acylation of phenols, thiophenol, amines and alcohols in a solvent-free system

“…Acid catalyzed acylation mainly requires polymeric acids [12,13]; and metal chlorides [14][15][16], metal triflates such as Sc(OTf)3/Bi(OTf)3/Li(OTf)3 [17][18][19], metal perchlorates (LiClO4 /BiOClO4) [20,21] have also been utilized as Lewis acid catalysts for acylation of alcohols. Other reagents such as I2 [22,23], [bmIm][dca] ionic liquid [24], solid supported reagents like HClO4-SiO2 [25], Py/basic alumina [26], neutral Al2O3 [27], Clay [28,29], ZrOCl2·8H2O [30] polyphosphate ester [31] and very recently ZnO [32], Sm [33] and Mg(NTf2)2 [34] have been employed for the same purpose. In this paper, we are describing our work on the successful use of non-toxic, environmentally benign and inexpensive zinc dust as a catalyst for the acylation of phenols, thiophenol, amines and alcohols with acid chlorides.…”