## 2 Results and Discussion  
### Chemistry  
In continuation of our previous work on the development of an effective strategy for the synthesis of antibacterial compounds [25], we have become interested in finding the chemoselective pathway of 2-(1\(H\)-indol-3-yl)-1\(H\)-benzo[\(d\)]imidazole derivatives [26]. We have previously shown that the condensation of anthranimalides with aldehydes on heating in \(N\),\(N\)-dimethylacetamide (DMAC) in the presence of sodium metabisulfite leads to the formation of antibacterial 2-(1\(H\)-indol-3-yl)quinazolin-4(3\(H\))-ones and their analogs. In the present study, we have expanded the scope of this reaction to obtain 2-(1\(H\)-indol-3-yl)-1\(H\)-benzo[\(d\)]imidazole derivatives **3** (Scheme 1). As shown in Scheme 1, we investigated the substrate scope of substituted indole-3-carboxaldehyde **1** starting with varying the substituents on the nitrogen atom of the indole ring. Aliphatic substituents, benzyl, and phenyl were well tolerated under this protocol and resulted in the corresponding products **3b**-**g** in 79-98% yields. Target compounds **3h**-**m** containing a substituent at the C(2) atom of the indole moiety have been obtained in good yields. A slightly reduced yield was observed for functionalized indices that had _para_-nitrophenyl and thienyl groups (**3i**, **3k**). 5-Substituted indoles **1n**-**p** were converted to the corresponding benzimidazoles **3n**-**p** in excellent isolated yields (92-97%). Next, the scope of the protocol was investigated using substituted phenylenediamines. The reaction was well suited for diamines containing halogens **2b**-**d**, **1**, **1**, **o**, **q**; methyl **2e**, **h**, **k**, **m**, **p**; and for \(N\)-substituted starting substrates **2r**-**v**. Target products **3q**-**t**, **w**, **x**, **z**-**ab**, **ad**-**ah**, **aj**, and **3 ak** were isolated as the sole product in good to excellent yields (72-97%). Surprisingly, the CF\({}_{3}\)- and NO\({}_{2}\)-substituted 2-(1\(H\)-indol-3-yl)-1\(H\)-benzo[\(d\)]imidazoles **3u** and **3y** were formed as mixtures of two isomers with a total yield of 52% and 63%, respectively (Scheme 1). The observed reactivity of unsymmetrical phenylenediamines is described in the literature [27; 28]. In the case of a methoxy group in the benzene ring and an allyl group at the nitrogen atom, we observed the formation of benzimidazoles **3v**, **ac**, and **3 ai** with a slightly decreased yield (51%, 57%, and 53%), together with a mixture of unidentified by-products. The method proved to be applicable to compounds of more challenging architecture such as 4\(A^{\prime}\)-methylenedibenzene-1,2-diamine (**2w**) and phenazine-2,3-diamine (**2x**). As a result of the cyclocondensation reaction of tetramine **2w** with 1\(H\)-indole-3-carboxaldehyde (**1a**), the bis-derivative **3a**l was obtained in an excellent yield of 95%. The phenazine-2,3-diamine (**2x**) offered corresponding imidazole **3 am** in a 60% yield. This choice was not accidental, since phenazine derivatives are distinguished by strong bacteriostatic properties [29]. The scope and limitations were investigated with respect to the synthesis of a variety of polysubstituted benzimidazoles. The target compounds **3 an**-**3 ar** were obtained in 64-96% yields. The limits of the applicability of the present protocol were expanded to various heterocyclic aldehydes **1** as starting substrates. As shown in Scheme 2, a wide range of heterocyclic aldehydes **1**, such as benzofuran-2-carbaldehyde, furfural, thiophene-2-carbaldehyde, 1-methyl-1\(H\)-pyrrole-2-carbaldehyde, isonicotinamidedehyde, and pyrazolecarbaldehyde, gave good yields of respective products. The cyclohexancerabldehyde **1w** provided the product **3 ay** with a yield of 65%. 2-Aminothiophenol (**2y**) reacted with 1\(H\)-indole-3-carboxaldehyde(**1a**) with the formation of benzo[_d_]thiazole **3 az** in an 87% yield.