The photoaddition of 4-hydroxycoumarin andN-methyl-4-hydroxyquinol-2-one to cyclohexene.

Divergent Photosensitizer Controlled Reactions of 4‐Hydroxycoumarins and Unactivated Olefins: Hydroarylation and Subsequent [2+2] Cycloaddition

“…Internal olefins and 1,1‐disubstituted olefins are also viable substrates ( 13 – 16 ). Of note, cyclohexene reacted smoothly to deliver the desired hydroarylation product 13 in 96 % yield without formation of the [2+2] cycloaddition product that was observed in the literature, [10b] highlighting the complementary reactivity of our approach to the prior work where UV irradiation was employed. The low yield of 16 was attributed in part to the volatile nature of the olefin.…”

“…Interestingly, one of the two lactone moieties in the cycloaddition product 4 could be selectively hydrolyzed upon treatment with piperidine in methanol, [10b] leading to chroman‐2‐one derivative 4 a in good yield (eq. 1.…”

Synthesis of 3,3′-methylenebis(4-hydroxyquinolin-2(1H)-ones) of prospective anti-COVID-19 drugs

“…3,3′-Methylenebis(1-ethyl-4-hydroxyquinolin-2(1 H )-one) ( 3g ) [ 26 ]. Orange crystals (DMF/EtOH), yield ( method a ): g 0.340 (87%) or yield ( method b ): 0.300 g (77%); IR (KBr): ν = 3500 (OH), 3030 (Ar–CH), 2867 (CH-Aliphatic), 1643 (CO), 1458 cm −1 (CH 2 ); 1 H NMR (400 MHz, DMSO- d 6 ): δ = 1.24 (t, 6H, CH 3- ), 3.89 (s, 2H, CH 2 ), 4.38 (q, 4H, CH 2 ), 7.00–7.05 (m, 2H, Ar–H), 7.29–7.35 (m, 2H, Ar–H), 7.59–7.70 (m, 4H, Ar–H), 7.90–8.07 (m, 2H, Ar–H), 12.65 ppm (s, 2H, OH); 13 C NMR (100 MHz, DMSO- d 6 ): δ = 12.95 (CH- 2 -Et), 21.11 (CH 2 ), 37.59 (CH 3 -Et), 108.52 (C-3), 115.15 (C-4a), 116.74 (C-8), 122.67 (C-6), 123.30 (C-5), 131.50 (C-7), 136.70 (C-8a), 159.63 (C-4), 164.83 ppm (C-2); MS (Fab, 70 eV, %): m/z = 390 (M + , 18), 202 (12), 136 (62), 120 (12), 107 (20), 89 (20).…”

“…Choudhary et al [ 25 ] synthesized some 3,3′-methylenebis(substituted-4-hydroxyquinolin-2(1 H )-ones from the condensation between two molecules of quinolones and one molecule formaldehyde but also neither mechanism nor NMR spectra were discussed for the products. Previously, irradiation of only N -ethyl(methyl)-4-hydroxyquinol-2-ones, was tested in ethanol and afforded their corresponding 3,3′-methylenebis(substituted-4-hydroxyquinolin-2(1 H )-ones, virtually eliminating the solvent as a source of formaldehyde [ 26 ]. The method suffered from low yields of the obtained products besides to its hazard condition.…”

Photoreaktionen von 3‐substituierten Cumarinen

“…Rislier sind in der Cumarin-Keihe photochemische Cycloadditionen von Tetrametliylathylen, Cyclopenten und Ketendiiithylacetal an unsubstituiertes Cumarin 41 sowie van Cyclohexen an 4-Hydroxycuniarin [5] beschrieben worden. Rei 3-substituierten Cumarinen sind ilagegen nur Cyclodimerisierungen bekannt ~21.…”