A mild and metal-free protocol for visible-light induced intramolecular radical cyclization of N-allyl(propargyl)-2-bromo-2,2-difluoro-N-arylacetamide has been developed.

A visible-light-induced radical tandem cyclization/arylation between 2-amino-1, 4-naphthoquinone and N-allyl-2bromo-2,2-difluoroacetamides has been developed without an external photocatalyst. The transformation could be carried out at room temperature and gave a variety of C-3-functionalized 2-amino-1,4-naphthoquinone derivatives in moderate to excellent yields. Moreover, mechanistic studies revealed that the reaction is driven by the formation of an electron donor−acceptor (EDA) complex.

A mild and efficient protocol for visible-light and organoamine cocatalyzed difluoroalkylation of quinoxalin-2(1H)-ones with functionalized difluoromethyl bromides has been developed. The transformation could be carried out at room temperature and gave a variety of C-3 difluoroalkylated quinoxaline-2(1H)-ones in moderate to excellent yields. More-over, mechanistic studies revealed that this transformation proceeded through a radical-type debrominative coupling process with only need of catalytic amount of diisopropylethylamine (DIPEA). This strategy featured wide functional group tolerance, excellent regioselectivity, mild conditions, and operational simplicity. [a] Dr. Scheme 1. Strategies for the synthesis of quinoxalin-2(1H)-one derivatives and examples of difluoroalkyated pharmaceutical.oaceate (5.0 mmol) and amine (6.0 mmol). The mixture was stirred at room temperature under N 2 atmosphere. After the amine was exhausted, the crude product was purified by chromatography on silica gel to afford the desired substrate 2.General procedure for the synthesis of 3. A 10 mL Schlenk bomb was charged with fac-Ir(ppy) 3 (1.25 umol), 1 a (0.25 mmol), 2 a (0.5 mmol), K 2 CO 3 (0.5 mmol), DIPEA (0.025 mmol) and MeCN (1 mL). The reaction mixture was then stirred under N 2 atmosphere with irradiation of 3 W blue LEDs at room temperature for 12 h. Subsequently, the mixture was quenched with water (15 mL) and extracted with CH 2 Cl 2 (10 mL × 3). The combined organic phase was dried over anhydrous MgSO 4 and evaporated to give a residue, which was purified by column chromatography on silica gel using petroleum ether/ethyl acetate (30 : 1) as an eluent to give pure products 3 aa as a white solid.

A novel visible‐light‐driven decarboxylative coupling of alkyl N‐hydroxyphthalimide esters (NHP esters) with quinoxalin‐2(1H)‐ones has been developed. This C(sp2)−C(sp3) bond‐forming transformation exhibits excellent substrate generality with respect to both the coupling partners. Of note, a series of 3‐primary alkyl‐substituted quinoxalin‐2(1H)‐ones that were difficult to synthesize by previous methods could be obtained in moderate to excellent yields. Additionally, the mild conditions, easy availability of substrates, wide functional group tolerance and operational simplicity make this protocol practical in the synthesis of 3‐alkylated quinoxalin‐2(1H)‐ones.

A green, sustainable, and straightforward method for the synthesis of unsymmetrical oxalamides via photoinduced C–N/CO bond formation of bromodifluoroacetamide, amine, and H2O through a triple-cleavage process has been developed. In addition, this approach also provides access to the known bioactive compounds, and a feasible reaction mechanism is proposed. Moreover, the advantages of this transformation, including mild reaction conditions, a broad substrate scope, and operational simplicity, make this protocol attractive for further applications.