Novel tricyclic 4H-imidazo[4,5-b]quinoxalines were synthesized by a new ortho-annulation process starting from 4H-imidazoles and cerammonium nitrate (CAN) as oxidation reagent in the presence of potassium carbonate as base. This reaction is interpreted as a multi-step reaction involving oxidative radical formation, a radical aromatic substitution and a subsequent redox process. The analysis is supported
在碳酸钾为碱的存在下,以4 H-咪唑和硝酸铈铵(CAN)为氧化剂,通过新的邻位环化工艺合成了新型三环4 H-咪唑并[4,5- b ]喹喔啉。该反应被解释为涉及氧化自由基形成,自由基芳族取代和随后的氧化还原过程的多步骤反应。高级DFT计算支持该分析。这种新颖的转化为吡嗪的环稠合衍生物的构建开辟了道路。新的三环产品在溶液中显示出强荧光,此外还显示出可逆的氧化还原活性。 胺-杂环-氧化-自由基反应-闭环
Synthesis and Structure of Thia and Selena Heterocycles Containing Cycloamidine Substructures
Cyclization of a bis-arylimidoyl chloride with an acylselenourea leads to the construction of a 1,3-selenazolidine with a heteroradialene structure. Another reaction of the bis-arylimidoyl chloride (hydrazinolysis) leads to the formation of Î2-1,2-diazetines, which we have shown previously to be reactive precursors for ring transformation reactions that yield unusual heterocycles. We now demonstrate that the reaction of these Î2-1,2-diazetines with various isothio- or isoselenocyanates affords an efficient entry to highly substituted 1,3,4-thia- or -selenadiazines. The structures of these novel derivatives were confirmed by NMR and mass spectroscopy, elemental analysis, and X-ray structural analysis. Detailed multidimensional 77Se NMR experiments as well as density functional theory (DFT) calculations show structural specifics of these compounds.
Vinylogous Tetraazafulvalenes: New Deeply Coloured Compounds Derived from Simple Amidines
作者:J. Brandenburg、C. Käpplinger、R. Beckert
DOI:10.1055/s-1996-4386
日期:1996.11
A one-step synthesis of vinylogous tetraazafulvalenes by simple cycloacylation of acetamidine 2 with bisimidoyl chlorides of oxalic acid 1 is described. The deeply coloured products 4a-i constitute a new class of stable neutrocyanines as well as compounds with indigoid properties.
was confirmed as a novel fluorubine derivative. In continuing our studies to substituted oligoazaacenes, we developed several synthetic entries to build up novel fluorubine derivatives, in which particularly aminobridged bis(quinoxaline)s are the key products for cationic hexaazapentacenes. We would like to discuss the possible formation pathways of these fluorubine derivatives, which exhibit interesting