Room temperature ionic liquid promoted regioselective synthesis of 2-aryl benzimidazoles, benzoxazoles and benzthiazoles under ambient conditions

An Inorganic Iodine‐Catalyzed Oxidative System for the Synthesis of Benzimidazoles Using Hydrogen Peroxide under Ambient Conditions

“…In view of the drawbacks of existing routes and the importance of green chemistry, a few green syntheses of benzimidazoles have recently been reported, employing air, [28] HClO (generated in situ from H 2 O 2 and HCl), [29] metal ions, [30] and ionic liquid. [31] However, even these methods still have several drawbacks from a practical point of view. These are: (i) the need for a high temperature (often > 100 8C) and long reaction time (up to 44 h); (ii) the use of strongly acidic conditions that may be detrimental to some sensitive substrates; (iii) the use of metal ions which, in addition to environmental concerns, often requires decomplexation of the metal from the product with the help of harmful reagents such as H 2 S; [13d, 30a, b] and (iv) complex routes for the synthesis of ionic liquids.…”

Synthesis of 2-Aryl Benzoxazoles from Aldoximes

“…The condensation of 2-aminophenol and carboxylic acid 17 or its surrogates such as aldehydes, [18][19][20][21] acid chlorides, [22][23][24] orthoesters, [25][26][27] and β-oxodithioesters 28 under various reaction conditions are the straight forward approaches to construct the benzoxazole unit. However, these methods are often associated with several limitations such as the use of highly toxic reagents, strong acids and, in some cases, harsh reaction conditions.…”

Boric Acid Catalyzed Synthesis of 2-substituted Benzoxazoles in Aqueous Media

“…Different catalysts and different methods were also reported for the synthesis of these heterocycles like Pd(OAc)2 [12], ZrOCl2 . 8H2O [13], silica sulfuric acid [14], silica supported sodium hydrogen sulfate [15], Indian 190 resin [16], ([Hbim]BF4) [17], methane sulphonic acid [18], Cu(OTf) 2 [19], copper (II) oxide nanoparticles [20], PCC-supported silica gel [21], In(OTf)3 [22], SnCl2 [23], DDQ [24], BF3 . OEt2 [25], Mn(OAc)3 [26], PhI(OAc)2 [27], Th + ClO4 - [28], BaMnO4 [29], NiO2 [30] and Pb(OAc)4 [31].…”