Coumarins dihydro- from

Coumarin, 7-diethylamino-4-methyl-fluorescence, 3, 879 Coumarin, dihydro-chroman synthesis from, 3, 785 4H-chromene synthesis from, 3, 765 coumarin synthesis from, 3, 810 mass spectra, 2, 23 synthesis, 3, 848 Coumarin, 3,4-dihydro-4,4-disubstituted synthesis, 3, 754... 

Miscellaneous Reactions. Palladium dba has been employed as a catalyst for effecting various annulation reactions. Mediumsized nitrogen heterocycles have been prepared from allenes and amino alkenyl hahdes in the presence of a Pd(dba)2/PPh3 catalyst system. 1,3-Dienes can be converted to benzofuran derivatives upon reaction with o-iodoacetoxy arenes and this reaction has been applied in the synthesis of new coumarins. Dihydro-quinoxalines and quinoxalinones have been obtained via reductive annulation of nitro enamines (eq 26). ... 

The same Lewis acid has been applied also as a catalyst for the syntheses of 2,3-dihydro-1H-1,5-benzodiazepines in very good yields from o-phenylenendiamine and ketones [39]. Solvent-free coumarin [40] and porphyrin syntheses have also been reported [41]. 

Figure 11.4. PARP inhibitors nicotinamide, 5-methylnicotinamide,6-aminonicotinamide,picolin-amide, 3-methoxybenzamide, benzamide, 3-aminobenzamide, 2-aminobenzamide, 4-aminobenz-amide, coumarin, 3,4-dihydro-5-methylisoquinolinone (PD 1287631, 4-amino-l,8-naphthalimide, 8-hydroxy-2-methyl-3-hydroquina2olin-4-one, phenanthridinone, and 3-0-allQ lbenzamides. This figure is redrawn from Ref 33 and is used with permission.

Polyestrogens from plants (secondary metabolites, among them compounds containing isoflavone and dihydro[3.2-c]coumarin fragments) in nutrition 02CL282. 

Reduction of coumarins to the dihydro-derivatives has frequently been achieved, but a more efficient procedure has emerged from a new study of this conversion. The most effective method was catalytic reduction in ethanol at 150 °C and under a high pressure (1500 psi) of hydrogen of give mostly the 2-hydroxy-3-phenylbutanoate, which was readily cyclized with PPA to the dihydrocoumarin. Hydroboration of 3-arylcoumarins, followed by oxidation, gave isoflavanones the latter have been dehydrogenated (with DDQ) to isoflavones. A reaction of wide potential value is the selective hydrolysis by zinc and methanol of phenolic acetates in the presence of aUphatic acetate groups. 

Rosati, O., Curini, M., Marcotullio, M.C., Oball-Mond, G., Pelucchini, C., Procopio, A. 2010. Synthesis of 5-amino-l,10fc-dihydro-2Ff-chromeno[3,4-c]pyridine-2,4(3//)-diones from coumarins and cyanoacetamides under basic conditions. Synthesis Stuttgart (2) 239-248. 

These include the SSA-catalyzed synthesis of heterocyclic compounds such as xanthenes, coumarins, oxazoles, and so on. Xanthenes are of great therapeutic and biological interest on account of their many biological activities such as anti-inflanunatory, antiviral, antibacterial properties, and so on. Seyyed Hamzeh et al. (2008) carried out the SSA-catalyzed synthesis of aryl-14 f-dibenzo[fl,y]xanthenes from aldehydes and P-naphthol and 1,8-dioxo-octahydro-xanthenes from aldehydes and 1,3-dicarbonyl componnd such as dimedone under solvent-free conditions (Schemes 5.25, 5.26). Reactions were carried out at 80°C. Nazeruddin et al. (2011) documented an effective method for 9,10-dihydro-12-aryl-8 f-benzo[a]xanthenes-ll(12 f)-one derivatives in excellent yield and short reaction time using SSA under solvent-free conditions (Scheme 5.27). 

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