Novel Preparation of Benzimidazole using amidine hydrochlorides

There are various methods available for the synthesis of diversely substituted benzimidazoles. The one of the method is condesnsation of o-phenylenediamines with aldehydes or acids or amides under oxidative conditions and metal-catalyzed reactions.  Another known route is the coupling of o-haloanilines with aldehydes under Cu-catalyzed conditions.

There is interesting report by Peng and co-workers about the Cu-catalyzed synthesis of library of benzimidazole compounds in water.  They used (o-haloaryl)benzamidine derivatives as a key RM, Cu2O (5 mol%) as catalyst, DMEDA (10 mol%) as ligand and K2CO3 (2.0 equiv.) as a base.

I came across a very recent an another interesting report by Qu Y. et al. for the preparation of benzimidazole derivatives where amidine hydrochlorides or aryl amidines were coupled with o-haloanilines under Cu-catalyzed conditions. DMEDA was used a lignd and Cesium carbonate as a base.  Also, combinations of various ligands and base were screened to get the best combination for the highest yield when aryl amidines were used as a coupling partner. The only draw-back of the reaction could be the higher temperature (140-145 °C) and the best part of this methodology is the higher yield (upto 90%).

Practical one-pot conversion of aryl bromides into aromatic nitriles without Cyanide reagent

Most of the aromatic cyanation reactions involved use of Hazardous Cyanide reagents - Sodium Cyanide, Potassium Cyanide, Zinc cyanide etc under the Pd-catalyzed conditions. I came across an recent article by Ishii Genki et al for the conversion of aromatic bromides into aromatic nitriles without previous metal catalysts. The

In their findings, firstly they treated aromatic bromide (reactive ones) with Mg-turning and subsequently with DMF.  The complex/reactive intermediate thus obtained was treated with aq. NH3 and molecular iodine to deliver the corresponding aromatic nitriles in very good yields. Howver, for the weakly reactive bromides, they used isopropylmagnesium chloride·lithium chhloride complex to complete the conversion.

The same methodolgy has been extended for the conversion of β-bromostyrenes into aromatic cinnamonitriles.