One-step synthesis of furocoumarins via oxidative annulation of 4-hydroxycoumarins with DDQ

Facile Reagent‐Free Synthesis of Furo[3,2‐c]pyridinones and Their Polynuclear Analogues with DDQ as Precursor

“…Likewise, the N ‐arylated substrates 2j‐l offered their fused furans in good yields of 67‐76%. It was revealed that the electron‐donating ‐OMe group posed a limited impact on the cyclization efficiency here than in the oxidative annulation of 4‐hydroxycoumarins or ketones with DDQ reported previously by us . Besides, we would like to note that N ‐phenyl 4‐hydroxypyridin‐2‐one can also give its furan product with good yield.…”

“…With our successful progress on the construction of furan scaffold using DDQ as maleonitrile building block,‐ the general reaction conditions are using 3 equivalents of DDQ to achieve the oxidative cyclization at room temperature. Thus, a model reaction of N ,6‐dimethyl‐4‐hydroxypyridinone with DDQ (3 equiv) was attempted in several solvents such as ethyl acetate (EtOAc), acetonitrile (MeCN), nitromethane (MeNO 2 ), 1,2‐dichloroethane (DCE) and dichloromethane (DCM).…”

“…In recent years, 2,3‐dichloro‐5,6‐dicyanobenzoquinone (DDQ) has been developed as maleonitrile building block to generate a furan unit, the process of which involves the concurrent scission of the two C‐C bonds in the DDQ skeleton. We have ever disclosed only one example with relation to the construction of furo[3,2‐ c ]quinolinone using this protocol . By virtue of the similarity with furo[3,2‐ c ]quinolinones and synthetic challenge of furo[3,2‐ c ]pyridinones, we envisioned that under appropriate conditions, an oxidative annulation with DDQ may be realized by the employment of N ‐substituted 4‐hydroxypyridinones 1 as precursors.…”

Coumarin-Annulated Ferrocenyl 1,3-Oxazine Derivatives Possessing In Vitro Antimalarial and Antitrypanosomal Potency

“…Synthesis of the target compounds was achieved by reductive amination of formyl hydroxycoumarins 9 and 14a – c with ferrocene methylamines 10a , b , prepared according to literature methods [ 13 , 51 , 52 , 53 , 54 ], that was affected by sodium borohydride as the reducing agent in yields ranging between 66 and 86% ( Scheme 1 ) [ 55 ]. Benzene-annulated hybrid compound 13 was readily obtained by cyclisation of the corresponding aminocoumarin-7-ol 11b under reflux with paraformaldehyde [ 46 ].…”

Solvent-, and Catalyst-free Acylation of Anilines with Meldrum's Acids: ANeat Access to Anilides

“…In our study on the synthesis of furo[3,2‐c]quinolinones, an unexpected decarboxylative reaction of N ‐substituted (Me, Et, Ph) anilines with Meldrum's acid provided the corresponding acetamides in low yields under neat condition at 80 o C. This finding prompted us to further investigate this transformation, in hope of developing a new efficient strategy to access amides with CO 2 and acetone as the only by‐products.…”