N 2 -C 3 Bonds Variant EIq

It should be noted that the examples of E-type formation of bonds in imidazo[l,5-a] quinoxalines are limited to variant EIq. The three-component reaction of 3-benzoylquinoxalin-2(l//)-one 34a with aromatic aldehydes and NHjOAc in boiling methanol is the only example of Eg-lype synthesis of the imidazo[l,5-a] quinoxaline system (Mamedov et al. 2011). This reaction leads not only to imidazo [l,5-fl]quinoxaline derivatives 12a and 67a-g but also to 2,4,5-trisubstituted imidazoles 68a-h, sometimes as major products. It should be noted that the reaction of A-alkylated 3-benzoylquinoxalin-2(lfl)-one 34i yields only imidazo[l,5-a] quinoxaline 67g. As distinct from variant CIq of synthesis of imidazo[l,5-a] quinoxalines where aminomethyl derivatives are used to introduce the C(l)-N(2) fragment into 3-benzoylquinoxalin-2(lfl)-one, in this case the reaction involves 

3 Synthesis of lmidazo[l,5-a]quinoxalines Based on Imidazole Derivatives 

Design of the imidazo[l,5-a]quinoxaline system on the basis of imidazole derivatives has been much less studied than the synthesis based on quinoxaline derivatives. Three variants of assembly of such a tricyclic system are mainly used intramolecular cycUzation of imidazole derivatives with formation of the C(4)-N(5) and C(9a)-N(10) bonds (variants A2i and A4i, respectively) and intermolecular condensation with equivalents of monoatomic carbon synthons with the simultaneous formation of the C(3a)-C(4) and C(4)-N(5) bonds (variant Bli) (Fig. 4.4). Other routes are represented by single examples. 

As distinct from imidazo[l,2-a]quinoxaline derivatives for which the method of construction of the heterocycle through the formation of the C(3a)-C(4) bond is basic (see Sect. 4.5.1), there are only two publications describing the Ali-type synthesis of representatives of the tricyclic imidazo[l,5-a]quinoxaline system (Malamas et al. 

---