Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

• ]diazepines 26 using substituted 2-formylbenzoic acids 25, phenylenediamine and tetronic acid with water as solvent (Scheme 8). The mechanism leading to the formation of the final product 24 and 26 involves an initial condensation between tetronic acid and benzene-1,2-diamine to give enaminone A. An

Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies

• Grzegorz Mlostoń and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221

• as single stereoisomers (79% yield) [63]. The same reaction pathway was observed in reactions with aromatic 1,2-diamines. For example, starting with benzene-1,2-diamine, the corresponding 2-oxo-1,2,3,4-tetrahydroquinoxaline derivatives, analogous to 73, were obtained in high yields as Z-isomers

A facile synthetic route to benzimidazolium salts bearing bulky aromatic N-substituents

• Gabriele Grieco,
• Olivier Blacque and
• Heinz Berke

Beilstein J. Org. Chem. 2015, 11, 1656–1666, doi:10.3762/bjoc.11.182

• -diisopropylphenyl)benzene-1,2-diamine (7) and using 1,2-dichlorobenzene as the starting compound, the mono-substituted product was obtained. To avoid this complication 1,2-dibromobenzene had to be applied to eventually approach the preparation of 7. For 8 a reported synthetic procedure was used [48][49] consisting

• of nucleophilic aromatic substitutions (SNAr) of benzene-1,2-diamine at 2-chloropyridine (Scheme 1). Once all the different N1,N2-diarylbenzene-1,2-diamines were prepared a method had to be developed to build up the imidazolium salts by ring closure. 3-Cl and 4-Cl could principally be obtained from

• (pyridin-2-yl)-1H-benzo[d]imidazol-3-ium chloride (4-Cl). In a 125 mL two neck round-bottomed flask was weighed N1,N2-di(pyridin-2-yl)benzene-1,2-diamine (8, 300 mg, 1.14 mmol) and triethyl orthoformate (30 mL) was added and a fractional distillation apparatus equipped with a Vigreux column and a

A one-pot catalyst-free synthesis of functionalized pyrrolo[1,2-a]quinoxaline derivatives from benzene-1,2-diamine, acetylenedicarboxylates and ethyl bromopyruvate

• Mohammad Piltan,
• Loghman Moradi,
• Golaleh Abasi and
• Seyed Amir Zarei

Beilstein J. Org. Chem. 2013, 9, 510–515, doi:10.3762/bjoc.9.55

• -diaminobenzene, dialkyl acetylenedicarboxylates, and ethyl bromopyruvate forms pyrrolo[1,2-a]quinoxaline derivatives in good yields. Ethylenediamine also reacts under similar conditions to produce new pyrrolo[1,2-a]pyrazine derivatives. Keywords: acetylenedicarboxylates; benzene-1,2-diamine; ethyl bromopyruvate

• ). The 1H NMR and 13C NMR spectra of products 4b–h were similar to those of 4a, except for the ester moieties, which exhibited characteristic resonances in the appropriate regions of the spectrum. Substitution on the benzene-1,2-diamine was also found to be important. A methyl group provided good yields

• bromopyruvate under similar conditions to form pyrrolo[1,2-a]pyrazine derivatives (Scheme 2). Compounds 9a,b were fully characterized according to their elemental analyses and their IR, 1H NMR and 13C NMR spectra and MS. Conclusion In summary, the reaction between benzene-1,2-diamine and dialkyl

Gold-catalyzed oxidation of arylallenes: Synthesis of quinoxalines and benzimidazoles

• Dong-Mei Cui,
• Dan-Wen Zhuang,
• Ying Chen and
• Chen Zhang

Beilstein J. Org. Chem. 2011, 7, 860–865, doi:10.3762/bjoc.7.98

• to form α-diketones and aldehydes in good yields is presented. Further directed synthesis of quinoxalines and benzimidazoles, via the condensation of the resulting α-diketones and aldehydes with benzene-1,2-diamine, was achieved in high yields. Keywords: allene; benzimidazole; gold-catalysis

• /hydration and oxidative cleavage of allenes to form α-diketones and aldehydes, and the synthesis of quinoxalines and benzimidazoles via the condensation of the resulting α-diketones and aldehydes with benzene-1,2-diamine [45][46][47][48][49][50][51][52][53][54][55][56]. Results and Discussion Our initial

• of quinoxalines and benzimidazoles via the condensation of the resulting α-diketones and aldehydes with benzene-1,2-diamine was achieved in high yields. This reaction appears to proceed via oxidation/hydration and oxidative cleavage of the allene, and investigations into the mechanism of this