Facile and efficient aerobic one-pot synthesis of benzimidazoles using Ce(NO3)3·6H2O as promoter

A modern and practical laccase-catalysed route suitable for the synthesis of 2-arylbenzimidazoles and 2-arylbenzothiazoles

“…As has been observed previously inferior results were obtained while using methanol and ethanol as co-solvents, as they both showed a great deal of competitive formation of products 3 and 4. 7,12 Improved chemoselectivity was observed with DMF and acetonitrile; wherein we were able to minimize the formation of the 1-N-benzylated product 4 (Table 1). Thirdly, we explored the possible effect of the type of laccase used on selectivity of these reactions.…”

“…1). 12 Furthermore, compounds with benzimidazole moieties have been utilized in material science applications; they are oen used as membranes for fuel cells and in organic lightemitting diodes. 13 A related class of compounds, the benzothiazoles, are also an important class of aromatic heterocyclic compounds composed of a benzene ring fused to a thiazole ring where a thiazole ring is a ve membered ring made up of sulphur and nitrogen atoms.…”

“…Due to their numerous biological activities, development of efficient synthesis methods for benzimidazoles and benzothiazoles compounds has received a signicant amount of interest. 7,12,14 The conventional methods include condensationdehydration reaction of ortho-aminoaromatics with carboxylic acids and their derivatives under strong acid and high temperature conditions or condensation with aldehydes under oxidative conditions. 26,34 A number of oxidants have been used to catalyse these reactions, including iodine, peroxides, 1,4benzoquinone, nitrobenzene, cupric acetate, and (bromodimethyl)sulfonium bromide, and recent advances for benzimidazoles include procedures such as microwave assisted synthesis and solid phase synthesis.…”

Synthesis and Pharmacological Profile of Benzimidazoles

“…Rao and Smith et al independently reviewed the reaction between OPD and Aldehydes ( Figure 6) as a simple and efficient method to synthesize benzimidazoles [17,18]. Numerous methods are reported for the condensation of substituted OPD with aryl/alkyl/heterocyclic aldehydes catalyzed by different oxidizing agents or metal triflate such as Sc (OTf) 3 or Yb (OTf ) 3 [19], sulfamic acid [20], H 2 O 2 -HCl [21], FeBr 3 [22], PhI (OAc) 2 [23], LaCl 3 [24], H 5 IO 6 -SiO 2 [25], Ce (NO 3 ) 3 .6H 2 O [26], NaHSO 4 -SiO 2 [27], mercuric oxide [28], chloranil [29], manganese dioxide [30], and I 2 /TBHP [31] and more methods [32][33][34]. This method isolated excellent yields of 2-substituted benzimidazoles with alkyl, aryl, and heterocyclic substituted moiety ( Figure 6).…”

Graphene Oxide: An Efficient and Recyclable Nano Catalyst for the Synthesis of 2-Substituted Benzimidazoles from Aldehydes and Diamines at Ambient Temperature

“…The procedure revealed good-to-excellent yields, new economic and eco-friendly protocol avoiding of the use of toxic metal catalysts, as well as additional bases and oxidants. Additionaly Ce(NO 3 ) 3 .6H 2 O is a very convenient promoter for the reaction of 1,2-diaminobenzene with aldehydes, affording benzimidazoles in good-to-excellent yields after stirring for a few hours under an air atmosphere [33].…”