Journal
SYNTHESIS-STUTTGART
Volume 54, Issue 7, Pages 1857-1869Publisher
GEORG THIEME VERLAG KG
DOI: 10.1055/a-1638-5030
Keywords
chromeno[4,3-b]quinolines; imines; iodine; tandem reaction; aza-Diels-Alder reaction; oxidation
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Funding
- Departamento Administrativo de Ciencia, Tecnologia e Innovacion (Colombian Institute for Science and Research, COLCIENCIAS) [111574455595, 648-2017]
- Universidad de Antioquia [20730003-028-2018]
- Fondo Nacional de Financiamiento para la Ciencia y la Tecnologia y la Innovacion 'Francisco Jose de Caldas' [811]
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A novel tandem approach was developed for the efficient synthesis of substituted chromeno[4,3-b]quinolines under metal-catalyst-and photosensitizer-free reaction conditions. The method, based on an inexpensive I(2)/DMSO system, features mild conditions, high step-economy, and provides a new access to biologically important nitrogen- and oxygen-containing heterocyclic molecules.
A tandem approach was developed for the efficient synthesis of substituted chromeno[4,3-b]quinolines from arylamines and O -cinnamyl salicylaldehydes under metal-catalyst-and photosensitizer-free reaction conditions. Our protocol is based on an inexpensive I (2) /DMSO system in which molecular iodine first acts as a Lewis acid to promote the formation of the corresponding imine bearing the alkene moiety; then, this species fulfills a second role by catalyzing an intramolecular aza-Diels-Alder cycloaddition to generate the respective tetrahydrochromenoquinoline as an intermediate. Finally, the dual behavior of DMSO as an oxidant and as a solvent proved crucial at this stage, allowing the regeneration of I (2) and promoting the aromatization of the tetrahydrochromenoquinoline intermediates to yield the desired 7-aryl-6 H -chromeno[4,3-b]quinolines. This protocol is mild and easy to perform, features high step-economy (tandem process) and provides a new access to biologically important nitrogen-and oxygen-containing heterocyclic molecules.
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