Efficient Solvent-Free Synthesis of Benzothiazine-Fused Pyrrolo[3,4-c]coumarins: Cycloaddition Reactions between Coumarin-Based Dihydrobenzothiazoles and Isocyanides

Access to 4-Alkenylated Coumarins via Ruthenium-Catalyzed Olefinic C-H Alkenylation of Coumarins with Modifiable and Removable Directing Groups

The ruthenium-catalyzed activation of the C4 position of coumarins for coupling with acrylates was described using modifiable ketone as a directing group. The alkenylation reaction provided a direct approach to prepare previously inaccessible 4-alkenylated coumarins with operational simplicity and high atom-economy. This protocol also worked well with coumarin-3-carboxylic acids to unveil a rare instance of a tandem alkenylation/decarboxylation reaction. The potential value of this approach was further highlighted by the efficient synthesis of several heterocyclic fused coumarin derivatives.

Hantzsch-like synthesis of novel bis(hexahydroacridine-1,8-diones), bis(tetrahydrodipyrazolo[3,4-b:4′,3′-e]pyridines), and bis(pyrimido[4,5-b]quinolines) incorporating thieno[2,3-b]thiophenes

A novel series of bis(hexahydroacridine-1,8-diones), bis(tetrahydrodipyrazolo[3,4- b:4′,3′- e]pyridines), and bis(pyrimido[4,5- b]quinolines) incorporating a thieno[2,3- b]thiophene core via ether or ester linkages is prepared via a Hantzsch-like reaction.

Three-component reaction between substituted 2-(2-nitrovinyl)-phenols, acetylenedicarboxylate and amines: diversity-oriented synthesis of novel pyrrolo[3,4-c]coumarins

The diversity-oriented synthesis of pyrrolo[3,4-c]coumarins via FeCl₃-promoted three component reaction between substituted 2-(2-nitrovinyl)phenols, acetylenedicarboxylate and amines has been developed.

Coumarin-fused coumarin: antioxidant story from N,N-dimethylamino and hydroxyl groups

Two coumarin skeletons can form chromeno[3,4-c]chromene-6,7-dione by sharing with the C ═ C in lactone. The aim of the present work was to explore the antioxidant effectiveness of the coumarin-fused coumarin via six synthetic compounds containing hydroxyl and N,N-dimethylamino as the functional groups. The abilities to quench 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS(+•)), 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH), and galvinoxyl radical revealed that the rate constant for scavenging radicals was related to the amount of hydroxyl group in the scaffold of coumarin-fused coumarin. But coumarin-fused coumarin was able to inhibit DNA oxidations caused by (•)OH, Cu(2+)/glutathione (GSH), and 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH) even in the absence of hydroxyl group. In particular, a hydroxyl and an N,N-dimethylamino group locating at different benzene rings increased the inhibitory effect of coumarin-fused coumarin on AAPH-induced oxidation of DNA about 3 times higher than a single hydroxyl group, whereas N,N-dimethylamino-substituted coumarin-fused coumarin possessed high activity toward (•)OH-induced oxidation of DNA without the hydroxyl group contained. Therefore, the hydroxyl group together with N,N-dimethylamino group may be a novel combination for the design of coumarin-fused heterocyclic antioxidants.