Organophotocatalytic Functionalization of 3,4-Dihydroquinoxalin-2-ones with Isoxazol-5-amines Using Visible Light

An organophotocatalytic strategy for the functionalization of 3,4-dihydroquinoxalin-2-ones with isoxazol-5-amines is reported. Using commercially available organophotocatalysts under visible-light irradiation and mild reaction conditions, a series of 20 seven 3,4-dihydroquinoxalin-2(1H)-one derivatives bearing a 5-aminoisoxazol-4-yl moiety at C-3 have been synthesized. The alkylation of 5-aminoisoxazole proceeds in a chemoselective manner, affording substitution exclusively at the C-4 position of this heterocycle. This process was also scaled up to 1 mmol, revealing the formation of an isoxazol-2-one derivative as a byproduct. The mechanism of this transformation has also been investigated through steady-state luminescence quenching experiments among other techniques.