Vinyl radicals. Stereoselectivity in hydrogen atom transfer to equilibrated isomeric vinyl radicals.

Synthesis and adenosine receptors binding affinities of a series of 3-arylcoumarins

“…Compounds 1–9 were efficiently synthesized according to the synthetic strategy outlined in Scheme . Perkin condensation of different commercially available ortho ‐hydroxybenzaldehydes with a conveniently substituted arylacetic acid, using N,N′ ‐dicyclohexylcarbodiimide (DCC) as dehydrating agent, afforded the 3‐arylcoumarins 1–3 . In fact, these reaction conditions have been also found to be appropriate when the reagents encompass in their structure methyl, methoxyl, ethoxyl or halogen groups.…”

“…The organic layer was washed with sodium bicarbonate solution (50 ml, 5%) and then water (20 ml). The solvent was evaporated under vacuum, and the dry residue was purified by FC (hexane/ethyl acetate 9 : 1) to give the products 1 (mp 131–132°C), 2 (mp 139–140°C) or 3 (mp 98–99°C) as beige powders, in yields of 70%, 65% and 75%, respectively.…”

Free-Radical Rearrangements

“…The Z-E isomerization of these radicals is rapid; for vinyl the rate constant for inversion lies between 3 x 10 7 and 3 x 10 9 sec -1 at -180°C, whereas 1-methylvinyl inverts somewhat more slowly (7,75). Under similar conditions, the scavenging of the cis and trans isomers of 1-chloro-and l-bromo-2-phenylvinyls is partly stereospecific (747), but l-methyl-2-phenylvinyl, 2-methyl-l-phenylvinyl, and 1,2-diphenylvinyl radi cals generated from cis and trans precursors yield products that have com pletely lost their stereochemical memories (748)(749)(750). Structure 395 has been identified for a sterically crowded vinyl (76) and for vinyls having R x groups capable of delocalizing the unpaired electron, e.g., C 6 H 5 (743) and COOH (744).…”

Catalytic Activity of Sulfated and Phosphated Catalysts towards the Synthesis of Substituted Coumarin

“…Coumarin derivatives containing benzopyrones structure [5,6] are important heterocyclic organic compounds used in different applications such as the food industry [7], pharmaceuticals [8], as precursors for organic compounds [9], cosmetics [10], optical brighteners [11], and anticoagulants [12,13]. Coumarins have also merged into various biological purposes such as antibacterial [14] anticancer [15], antimicrobial [16], antioxidant [17][18][19] and antiinhibitor [20,21].…”