Condensations aldehydes with 1,2-phenylenediamines, potassium

The starting phenylenediamine (12) was prepared by reaction of a 2-fluoronitro benzene (9) with an aniline (10) in the presence of potassium fluoride and subsequent reduction of the nitro derivative (11). The resulting amine (12) was generally alkylated with an alkyl bromide in the presence of sodium iodide to obtain the intermediate (13). However, when bulky groups had to be introduced, the intermediate (13 ) was conveniently obtained by reductive amination of either aldehydes or ketones. Condensation of (13) with (phenylhydrazono)malonyl dichloride followed by reduction with zinc and acetic acid led to the 3-amino substituted benzodiazepines (15). 

Reactions of Thiophen Aldehydes and Ketones.— The Stobbe condensation of some thienylcarbonyl compounds with dimethyl methylsuccinate in the presence of potassium t-butoxide or sodium hydride gave predominantly the ( -half esters of (156), while condensation with dimethyl homophthalate gave predominantly the (Z)-half ester of (157). Thiophen-2-aldehydes were shown to add smoothly to a -unsaturated ketones and nitriles, under the catalytic influence of cyanides, to form (158) and (159), respectively. Thiophen-2-aldehydes have been condensed with aliphatic amines and phenylenediamine to give Schiff bases ... 

Mathew et al. (2011) synthesized (2E)-l-(lH-benzimidazol-2-yl)-3-phenylprop-2-en-l-ones. o-Phenylenediamine reacts with lactic acid to give 2(a-hydroxyethyl) benzimidazole, which on oxidation in presence of potassium dichromate produced 2-benzimidazoles. The chalcones were prepared with Claisen-Schmidt condensation by reacting 2-acetylbenzimidazole with appropriate aldehydes in the presence of a base. 

Kalirajan et al. (2010) synthesized a series of pyrazole derivatives of benzimidazole. Condensation of substituted o-phenylenediamine with lactic acid under microwave irradiation and further oxidation of the product with potassium dichromate gave intermediate 2-acetyl benzimidazole, which was then reacted with aromatic aldehydes. Finally the product was cyclized with hydrazine to form final product. 

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