Abstract
Reaction of 2-cyanothiomethylbenzimidazole 1 with an aromatic aldehydes in water under ultrasonic irradiation for 10–13 min gave the corresponding unsaturated nitriles 2a–h which is an efficient and simple method under green conditions. The unsaturated nitrile derivatives were obtained in 86–98% yield with a short reaction time without any tedious workup procedures.
Highlights
The importance of heterocycles in many fields of science can hardly be overstated and justifies a long-lasting effort to work out new synthetic protocols for their production [1]
Al-Kadasi and Nazeruddin reported that the condensation of 4-hydroxycoumarin with aromatic aldehydes in water under ultrasound irradiations at ambient temperature gave excellent yield of the desired products in shorter reaction time [17]
Synthesis of 2-amino-4,6-diphenylnicotinonitriles via fourcomponent reaction of malononitrile, aromatic aldehydes, acetophenone derivatives, and ammonium acetate in water under ultrasound irradiation is described by Safari et al [18]
Summary
The importance of heterocycles in many fields of science (including organic, inorganic, bioorganic, agricultural, industrial, pharmaceutical, and medicinal chemistry, as well as material science) can hardly be overstated and justifies a long-lasting effort to work out new synthetic protocols for their production [1]. In Digoxin, if the lactone group at 17th position is replaced with α,β-unsaturated nitriles (–C=C–CN group), there is no loss in biological activity [12, 13] (see Figure 1). Mukarram et al reported [15] that the condensation of p-substituted benzaldehyde with active methylene compounds gave the corresponding unsaturated nitrile derivative, that is, entacapone, which is used for treatment of Parkinson’s disease. Al-Kadasi and Nazeruddin reported that the condensation of 4-hydroxycoumarin with aromatic aldehydes in water under ultrasound irradiations at ambient temperature gave excellent yield of the desired products in shorter reaction time [17]. Synthesis of 2-amino-4,6-diphenylnicotinonitriles via fourcomponent reaction of malononitrile, aromatic aldehydes, acetophenone derivatives, and ammonium acetate in water under ultrasound irradiation is described by Safari et al [18]. Α,β-unsaturated nitriles, that is, 2-((1H-benzimidazol-2yl)thio)-3-arylacrylonitrile in aqueous medium
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