A metal-free, visible-light (blue LED: hν = 425 ± 15 nm) photoredox-catalyzed intramolecular cyclization reaction of N-biarylglycine esters to phenanthridine-6-carboxylates in water under an open air atmosphere at ambient conditions has been developed.
An atom-economical and environmentally benign synthesis of N-substituted carbazoles is described. This methodology afforded products in 90–120 minutes.
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.
A series of 3-nitro-4-aryl-2H-chromen-2-ones in good yield have directly been obtained from aryl alkynoate esters and nitrite by employing mixture of K2S2O8-nitrogen doped graphene as an oxidant in watery medium...
The peroxodisulfate-assisted three-component benzylation of coumarins with styrenes and KSCN to 3-(1-aryl-2-thiocyanatoethyl)-2H-chromen-2-one is reported for the first time. This reaction proceeds via the consecutive addition of SCN radical to styrenes...
A simple method for the synthesis of 2,4-aryl-4-((arylsulfonyl)methyl)-4H-benzo[d][1,3]oxazines using an easily accessible K2S2O8-activated charcoal mixture and thiols, respectively, as an oxidant and sulfonylating precursors has been described.
A Umemoto's reagent-free and cost-effective method for synthesis of trifluoromethylated benzoxazines by 9,10-phenanthrenedione visible-light photocatalysis is described in this article.
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