NAMED ORGANIC REACTIONS
* The Phillips reaction involves the condensation of ortho phenylenediamines with organic acids in presence of dilute mineral acids to furnish benzimidazoles.
* This method has the advantage that the benzimidazoles, which cannot be prepared by heating the components together, are obtained easily by using dilute acids at lower temperatures.
* Good yields are obtained with aliphatic acids.
* However the yield can be improved by carrying out the Phillips reaction in sealed tubes with aromatic acids also.
* Initially one of the amine group is acylated with the organic acid in presence of mineral acid to furnish an N-acylated compound. In the next step, the other nitrogen is also acylated by making bond with the carbonyl carbon of the first acyl group leading to ring closure.
1) Benzene-1,2-diamine can be condensed with acetic acid in presence of 4N HCl to give 2-methyl-1H-benzimidazole.
2) 2-phenyl-1H-benzimidazole can be prepared by carrying out the Phillips reaction in a sealed tube at 180oC