The reactions of 3-ethoxycarbonylmethylene-3,4-dihydroquinoxalin-2(1H)-one and its derivatives in the synthesis of benzodiazepines and benzimidazoles: reinvestigation, structural reassignment, and new insight

2,3-(Dibenzimidazol-2-yl)quinoxalines: Unexpected Dynamical Effect on Steady-State Electronic Absorption Spectra

We report on the electronic absorption spectra, conformational behavior, and intra- and intermolecular hydrogen bonds of 2,3-(dibenzimidazol-2-yl)-quinoxaline (DBIQ). The experimentally found strong solvent dependence of the absorption spectra of DBIQ solutions cannot be assigned to electronic excitations of the equilibrium ground-state DBIQ structure. Extended consideration including the nonequilibrium structures within the framework of ab initio molecular dynamics (MD) revealed the importance of torsion molecular motions not covered by the static case. The strong impact of solute-solvent hydrogen bonding on stabilization of these nonequilibrium structures and on conformational composition of DBIQ was demonstrated. A presence of twisted nonplanar geometries along the whole MD trajectory was shown to drastically influence not only energies but also characters of electronic excitations, resulting in a change of local π-π* character in a solution of 1,2-dichloroethane to charge-transfer character in polar dimethylsulfoxide.

Direct synthesis of 2-oxo-acetamidines from methyl ketones, aromatic amines and DMF via copper-catalyzed C(sp3)-H amidination

A convenient method for the synthesis of 2-oxo-acetamidines from methyl ketones using aromatic amines and DMF as nitrogen sources is reported via copper-catalyzed C(sp3)-H amidination. Various methyl ketones react readily with aromatic amines and DMF, producing 2-oxo-acetamidines in yields of 47 to 92%. This protocol features the simultaneous formation of C-N and C[double bond, length as m-dash]N bonds using DMF and aromatic amines as two different nitrogen sources. It thus provides an efficient approach to construct acyclic amidines via three C(sp3)-H bond amidination. Based on the preliminary experiments, a plausible mechanism of this transformation is disclosed.

Metal-free oxidative ring contraction of benzodiazepinones: an entry to quinoxalinones

Herein is reported a practical method for the construction of 3-benzoylquinoxalinones from benzodiazepinones in the presence of DMSO which serves both as a solvent and an oxidant.

Recent advances in the synthesis of benzimidazol(on)es via rearrangements of quinoxalin(on)es

The review describes all the quinoxaline-benzimidazole rearrangements as a whole and the new quinoxalinone-benzimidazol(on)e rearrangements in particular when exposed to nucleophilic rearrangements which can be used for the synthesis of various biheterocyclic motifs.

Rapid and Efficient Synthesis of a New Series of 2-Aryl-5-Fluoro-6-(4-Phenylpiperazin-1-Yl)-1H-Benzimidazoles Using Microwave Heating

A new series of 2-aryl-5-fluoro-6-(4-phenylpiperazin-1-yl)-1H-benzimidazoles was synthesised from the reaction of 4-fluoro-5-(4-phenylpiperazin-1-yl)benzene-1,2-diamine and iminoester hydrochlorides. 4-Fluoro-5-(4-phenylpiperazin-1-yl)benzene-1,2-diamine was prepared from the reduction of 5-fluoro-2-nitro-4-(4-phenylpiperazin-1-yl)aniline by using Pd/C (10%) catalyst and hydrazine hydrate under microwave irradiation. The structures of newly synthesised compounds were identified by 1H NMR, 13C NMR, mass spectroscopy and elemental analysis data.