A novel, visible-light-mediated method for the synthesis of 2-substituted benzothiazoles from thiophenols and alkyl/aryl nitriles in the presence of eosin Y under air atmosphere is disclosed.
A visible‐light photoredox cyclization of a series of N‐biarylglycine esters to phenanthridine‐6‐carboxylates using 9,10‐phenanthrenedione (PQ) as a catalyst, white LEDs (7 W) as irradiation source and oxygen from air as a terminal oxidant is described. Also, for the reaction, a feasible mechanism is proposed. The N‐biarylglycine esters are converted into radical intermediates by the action of an excited‐state catalyst (PQ*), which are subsequently subjected to intramolecular cyclization followed by dehydrogenation reactions in one‐pot to afford desired products in high yield. Use of inexpensive catalyst, short reaction time and in situ generation of N‐biarylglycine esters are some of the important advantages of present methodology while compared to rose bengal‐photocatalysted protocol already reported by us.
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