Potassium hydrogen sulfate: An efficient catalyst in organic reactions

Peroxy Compounds as Eco-Friendly Catalysts for Nitration of Aromatic Compounds Using Sodium Nitrite in Aqueous Bisulfate Medium

“…In the present study, KHSO4 creates an acidic environment due to the protolysis of the bisulfate ion (HSO4 -) followed by the release of a proton (H + ) without decomposition and thus acts as a pool of proton source. [36][37][38][39] Basically, all the peroxy compounds in this study are strong oxidizing agents, which may present as free radical or ionic species. The absence of free radical species, thus suggests the participation of either the ionic species or molecular species in the mechanism of generating active nitronium ion ingredient as shown in the following steps:…”

“…On the other hand, in the recent past, potassium bisulfate (KHSO4) is explored as an eco-friendly, inexpensive, non-toxic, and easy available efficient green catalyst for various organic transformations under homogeneous and heterogeneous conditions. 38,39 A review article published by Baghernejad 39 provides an excellent bibliography depicting an array of synthetic strategies in which KHSO4 is used as a catalyst. In many cases, the catalyst was recovered, activated and reused for three to four consecutive times with only slight variation in the yields of the products.…”

“…Ipso nitration of aryl boronic acids was reported 33 in aqueous media using NaNO2/Cu2O/aqNH3. Few acid-free nitration protocols [34][35][36][37][38][39][40][41][42] were also developed using NH4NO3/KHSO4, N2O5 and ClNO2, TBAD and TBAC with NaNO2, quaternary ammonium nitrate, N2O5/SO2, tertiary butyl nitrite, MeNO2 with K2CO3/Al2O3. The efforts of…”

Reactions of N-heterocyclic ligands with substitutionally labile organometallic complexes, [(η5-C5R5)Fe(CO)2E]BF4

“…DABCO is known mainly as an organic catalyst in a large variety of organic syntheses [25][26][27]. For example it has displayed high catalytic activity in the methylation of indole in conjunction with dimethyl carbonate [28].…”

Diazabicyclo[2.2.2]octane stabilized on Fe3O4 as catalysts for synthesis of coumarin under solvent-free conditions

“…1,4-Diazabicyclo[2.2.2]octane (DABCO), a cage-like compound, is a small diazabicyclic molecule with weak alkalescency and medium-hindrance [13]. DABCO has been applied as an inexpensive, eco-friendly, high reactive and non-toxic base catalyst for various organic transformations, including ring opening of aziridines with amines or thiols [14], oxidative deprotection of (tetrahydropyranyl) ethers and silyl ethers [15], conversion of tetrahydropyranyl ethers into acetates [16], regioselective nucleophilic aromatic substitution reaction [17], synthesis of isoxazolines [18], synthesis of N-arylphthalimides [19], synthesis of industrially important polyurethane foams [20], and Baylis-Hillman reactions [21,22].…”