Synthesis and Photophysical Properties of 1,4-Dihydro-2H,5H-chromeno[4,3-d][1,3]oxazin-5-ones, and Derivatives Containing Tethered 1,2,3-Triazoles, from 4-Aminocoumarins

DILELIO, MARINA; BRITES, NATHAN; VIEIRA, LARISSA; IGLESIAS, BERNARDO; KAUFMAN, TEODORO; SILVEIRA, CLAUDIO

SYNTHESIS-STUTTGART

GEORG THIEME VERLAG KG

Lugar: Stuttgart; Año: 2019

0039-7881

A facile protocol for the unprecedented one-pot H2SO4-mediated hydroxymethylation/cyclative N,O-acetalization of 4-aminocoumarins toward 1,4-dihydro-2H,5H-chromeno[4,3-d][1,3]oxazin-5-ones, in moderate to good yields, was developed and optimized. The scope and limitations of the transformation, which takes place in water or water/THF mixtures, were also studied. The nitrogen atom of the resulting tricycles was used to tether alkyl, aryl and 1,2,3-triazolylmethyl moieties, employing a two-step click chemistry approach for the latter. The photophysical properties of the heterocycles as well as those of their 1,2,3-triazole derivatives were also examined. The N-aryl derivatives exhibited high quantum yields of fluorescence (up to Öf =0.69) and very large Stokes shifts (up to 201 nm).