Formic acid and its salts

(A) Wang et al. reported a facile three-component condensation for the synthesis of quinazolin-4(3H)-ones.¹⁰ In this synthesis several quinazolin-4(3H)-ones were generated in good yield by the ytterbium complex mediated, solvent-free, one-pot reaction of anthranilic acid, formic acid, and amines. (Equation Presented) (B) Lin et al. discovered formic acid catalyzed dimerization of stilbenes to tetralin derivatives.¹¹ In this reaction the stereo defined tetralin derivatives were obtained by formic acid mediated dimerization of some stilbenes having activated aromatic rings. (Equation Presented) (C) Gowda et al. reported the zinc dust catalyzed reductive cleavage of azo-compounds to corresponding amines using ammonium formate or formic acid.¹² In this reaction the azo-compounds were cleaved to amine by ammonium formate or formic acid in the presence of a catalytic amount of zinc dust in methanol. Furthermore, during course of the reaction sensitive functional groups like OH, CH₃, OCH₃, COOH, COCH ₃, etc. were not affected. (Equation Presented) (D) Recently, our group reported the utilization of ammonium formate for the generation of 2,5-diphenylpyrrole from the corresponding 2-butene-1,4-dione and 2-butyne-1,4-dine.^9a,d In this one-pot microwave-mediated 'green chemistry' reaction, ammonium formate was used as the source of hydrogen and ammonia for the synthesis of pyrrole derivatives. (Equation Presented) (E) We also reported the utilization of formic acid for the generation of 2,5-diphenylfuran from the corresponding 2-butene-1,4-dione and 2-butyne-1,4-dione.^9b In this facile one-pot microwave-mediated reaction, formic acid was used as the source of hydrogen and the acid catalyst for the generation of furan derivatives. (Equation Presented) (F) Furthermore, unprecedented oxidation properties of formic acid were found in the conversion of 1,2,3,4-tetraphenyl-2-butene-1,4-dione to benzil.^9e In this facile transformation conducted under microwave conditions, formic acid behaves as an oxidizing agent in contrast to its well-known behavior as a reducing agent or an acid catalyst. (Equation Presented).