A New Synthesis of 3,4-Dichlorocoumarins¹

Regioselective Chlorination and Suzuki–Miyaura Cross‐Coupling of 4‐Alkoxycoumarins, 4‐Alkoxy‐2‐pyrones, and Related Heterocycles

“…3‐Chloro‐4‐methoxycoumarin (2a): Coumarin 1a (2.0 g, 11.35 mmol) was used in the general procedure to give 2a (1.377 g, 58 %) as a cream‐colored solid. M.p.…”

“…The filtrate was concentrated under reduced pressure, and the resulting residue was recrystallized from EtOH to yield the product. [34] Coumarin 1a (2.0 g, 11.35 mmol) was used in the general procedure to give 2a (1.377 g, 58 %) as a cream-colored solid. M.p.…”

“…84-85°C; ref. [34] [12] Coumarin 1b (1.0 g, 4.20 mmol) was used in the general procedure to give 2b (0.727 g, 64 %) as a pale orange solid. M.p.…”

Synthesis and reactions of halogen-containing chromones

“…The reduction of 3,4-dichlorocoumarins, prepared by treatment of phenols with perchloropropylene in the presence of aluminium chloride, 35 with lithium tri(tert-butoxy)aluminium hydride produces lactols, which are easily transformed into 3-chlorochromones 10a ± c when heated in acetic acid in the presence of catalytic amounts of H 2 SO 4 . 36,37 When chromone 1a is subjected to oxidative chlorination (m-chloroperbenzoic acid, HCl, DMF, *20 8C), 3-chlorochromone 10a is formed in 96% yield.…”

Revised Structure by Computational Methods for a Coumarin Isolated from Zanthoxylum Rhoifolium (Rutaceae)

“…First, despite the fact that hydroxy-and methoxycoumarin are important components of many synthetic and natural products, natural coumarins lacking an oxygen functionality on the aromatic ring and having pyrone ring substitutents, so called simple coumarins, are quite rare [6][7]. In fact, few examples of natural, simple coumarins are known [5,[8][9][10][11], but a much larger number of synthetic ones have been prepared [3,[12][13][14][15][16][17][18][19][20]. Secondly, many biologically active coumarins bearing an oxygen functionality at C-4 occur widely among natural products.…”