Revisiting the three component synthesis of isoxazolo[5, 4-b]pyridines, 4-aryl-3, 7, 7-trimethyl-isoxazolo[5, 4-b]quinolin-5(6H)-ones and related heterocycles. (14th December 2016)

• Record Type: Journal Article
• Authors: Lingham, Anthony R.; Hawley, John A.; Greaves, Tamar; Jackson, Neale; Antolasic, Frank; Hügel, Helmut M.
• Is Part Of: Polyhedron. Volume 120(2016)
• Page Start: 175
• Page End: 179
• Publication Date: 2016-12-14
• Subjects: Multicomponent microwave synthesis -- Knoevenagel -- Isoxazolopyridines -- Isoxazoloquinolinones -- Tetrahydroacridones; Chemistry, Inorganic -- Periodicals; Chimie inorganique -- Périodiques; Organometaalverbindingen; Anorganische chemie; 546.05
• DOI: 10.1016/j.poly.2016.09.011
• Languages: English
• ISSNs: 0277-5387

Abstract

Graphical abstract: The one-step three-component microwave assisted synthesis between aromatic aldehydes with tetronic acid or 1, 3-indandione readily produced Knoevenagel adducts that underwent addition of 3-methylisoxazol-5-amine (1 ) to form the isoxazolopyridine products (8 ). With dimedone, the Knoevenagel adduct was generated using 2-hydroxyammonium formate and then reacted with1 to give pure products. Abstract: The one-step three-component microwave assisted synthesis between aromatic aldehydes with tetronic acid or indan-1, 3-dione readily formed the Knoevenagel adducts that underwent addition of 3-methylisoxazol-5-amine1 to form the isoxazolo[5, 4- b ]pyridine products8 [a, b, d, e, g ] in 67–90% yield. The multicomponent reaction using dimedone formed the respective addition products 4-aryl-3, 7, 7-trimethyl-isoxazolo[5, 4- b ]quinolin-5(6 H )-ones8 [c, f, h ] (36–79%). In contrast, the sonication of an aryl aldehyde and dimedone with an equivalent amount of 2-hydroxyammonium formate exclusively generated the Knoevenagel adduct4c viahydro -4c . When microwaved either with 3-amino-5-methylisoxazole1 or 3, 4, 5-trimethoxyaniline14 in ethanoic acid–ethylacetate (1:1), tetrahydroacridones15 [a, b ] formed in high yields (88–92%). Importantly, this two-step reaction sequence generates highly reproducible and pure products.