Synthesis of heteroannulated 3-nitro- and 3-aminopyridines by cyclocondensation of electron-rich aminoheterocycles with 3-nitrochromone

Domino Reactions of Chromone‐3‐carboxylic Acids with Aminoheterocycles: Synthesis of Heteroannulated Pyrido[2,3‐c]coumarins and their Optical and Biological Activity

“…Our starting point was the development of suitable conditions for the synthesis of pyrido[3,2‐ c ]coumarin 3a by reaction of chromone‐3‐carboxylic acid 1a with aminopyrazole 2a (Scheme ). The aminopyrazole 2a and related aminoheterocycles used in this study were prepared as previously reported in our work related to the synthesis of heteroannulated pyridines, spirocyclic 1,4‐dihydropyridine compounds, and 3,4‐fused coumarins . The best yield of 3a (up to 90 %) was obtained under the conditions reported in entry 5 of Table using acetic acid as solvent (14 h, 60 °C).…”

(β‐D‐Ribofuranosyl)formamidine in the Design and Synthesis of 2‐(β‐D‐Ribofuranosyl)pyrimidines, Including RF‐Containing Derivatives

“…It is known that 3-nitro-and 2-methyl-3-nitrochromones [22] react with amidines and guanidine to give the corresponding 5-nitropyrimidines. [23] These reactions proceed by nucleophilic 1,4-addition followed by pyrone ring opening and intramolecular condensation at the carbonyl group.…”

“…The reduction of the nitro group of these compounds by hydrogenation in the presence of Pd/C (10 mol-%) afforded the expected 5-aminopyridines 10a-c in quantitative yield. [22] Li, Duan and Hu [24] condensed 3-iodochromone with phenylacetylene and amidines to give (5Z)-5-benzylidene-5H-chromeno [4,3-d]pyrimidines, the configuration of which was unambiguously established as the Z form from X-ray diffraction analysis. Following this precedent for the use of 3-alkynylchromones in pyrimidine synthesis, 3-(phenylethynyl)chromone was treated with C-glycosyl amidine 3 in the presence of K 2 CO 3 and molecular sieves in DMF to produce benzopyrano [4,3-d]pyrimidine 11, with a glycosyl moiety attached at C-2.…”

Ring Opening and Recyclization Reactions of 3‐Nitrochromone with Some Nucleophilic Reagents

“…Elemental microanalyses were performed on a Perkin‐Elmer CHN‐2400 analyzer at the Chemical War Department, Ministry of Defense, Egypt. 3‐Nitrochromone ( 1 ) was prepared according to a literature method .…”

“…3‐Substituted chromones are very active substrates for nucleophilic attack at C‐2 position and used as valuable synthetic intermediates in the preparation of a variety of heterocyclic compounds . 3‐Nitrochromone has received attention as building blocks for construction of a diversity of heterocycles especially heterannulated 3‐nitropyridines via its reactions with some electron‐rich heterocyclic enamines . In the present work, we aimed to study the chemical reactivity of 3‐nitrochromone ( 1 ) towards some mono‐nucleophilic and bi‐nucleophilic reagents that have never been studied before.…”