Pyrido benzimidazole, formation

Dzvinchuk has synthesized several pyrido[l,2-a]benzimidazoles (84, 86 and 88) via reactions of 2-acylmethylbenzimidazole 82 (Scheme 17). Treatment of 82 with malononitrile led to the formation of the dicyanomethylene-... 

Scheme 42 Formation of pyrido[1,2-a]benzimidazoles from aminopyridines and arenas.

When 2-halophenyl pyridyl amide anions such as 109 are irradiated in liquid ammonia, pyrido[l,2-a]benzimidazoles 110 were obtained with good yields through a new C—N bond formation (Eq. 10.37) [82] ... 

Senn-Bilfinger J, Kruger U, Sturm E, et al. (H -K )-ATPase Inhibiting 2-[(2-Pyridylmethyl)sulfinyl]benzimidazoles. 2. The reaction cascade induced by treatment with adds, formation of 5H-pyrido[T,2 4,5][1,2,4]thiadiazino[2,3-a]benzimidazol-13-ium salts and their reactions with thiols. J Org Chem 1987 52 4582-4592. 

Another application of catalytic hypervalent iodine(in) was developed in the synthesis of pyrido[l,2-a]imidazoles 160 (Scheme 39). The I(III) generated from catalytic iodobenzene and peracetic acid catalyzed the C-H cycloamina-tion of N-ary 1-2-aminopyridines 161 produced diversified N-heterocycles 160 [55]. In another hand, the same products were prepared from N-benzyl-2-aminopyridines 162. The conversion of N-benzyl-2-aminopyridines 162 into pyrido[l,2-a]benzimidazoles involve tandem demethylation and C-N bond formation to afford the desired products in good yields [56]. 

In 2010, Zhu and coworkers first reported the direct intramolecular C(sp )-H amination of Af-arylpyridine-2-ammes using a combination of Cu(OAc)2 and Fe(N03)3 as a bimetalUc catalytic system to furnish pyrido[l,2-a]benzimidazoles in satisfactory yields [13]. The authors believe that a Cu(lll)-catalyzed electrophilic aromatic substitution (SEAr) pathway is operating in this process according to the results of mechanistic studies, wherein iron(lll) acts a unique role to facilitate the formation of the more electrophilic Cu(III) species because in the absence of iron(III), a much less efficient and reversible Cu(II)-mediated SEAr process takes place. 

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