CLXVI.—Hydroxy-carbonyl compounds. Part III. The preparation of coumarins and 1 : 4-benzopyrones from phloroglucinol and resorcinol

Preparation of highly superacidic sulfated zirconia via combustion synthesis and its application in Pechmann condensation of resorcinol with ethyl acetoacetate

“…However, the acid-catalyzed Pechmann reaction is a simple and commonly used method for synthesizing coumarins from activated phenols, mostly m-substituted phenols containing electrondonating substituents at the m-position and b-keto-esters or an unsaturated carboxylic acid [28,29,48]. Conventionally, the Pechmann reaction is carried out in the presence of concentrated sulfuric acid catalyst [30,49], phosphorus pentoxide [50], trifluoroacetic acid [51], and aluminum chloride [52]. These acids are corrosive and required in excess.…”

Copper(I)‐Catalyzed 3‐Position Methylation of Coumarins by Using Di‐tert‐butyl Peroxide as the Methylation Reagents

“…3,6,8-Trimethyl-2H-chromen-2-one (3h) Column chromatography on silica gel (ethyl acetate/petroleum ether 1∶32 to 1∶20) afforded the title product in 51% isolated yield as a white solid; 1 H NMR (400 MHz, CDCl 3 ) δ: 7.45 (s, 1H), 7.14 (s, 1H), 7.04 (s, 1H), 2.43 (s, 3H), 2.37 (s, 3H), 2.22 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ: 163.4, 150.5, 140.4, 134.1, 133.7, 126.2, 126.0, 125.2, 119.8, 21.5, 17.9, 16. [15] Column chromatography on silica gel (ethyl acetate/petro-leum ether 1∶32 to 1∶20) afforded the title product in 50% isolated yield as a white solid; 1 H NMR (400 MHz, CDCl 3 ) δ: 7.70 (s, 1H), 7.18 (d, J＝7.6 Hz, 1H), 6.97 (d, J＝7.6 Hz, 1H), 2.47 (s, 3H), 2.41 (s, 3H), 2.24 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ: 163.0, 152.7, 137.3, 133.1, 132.2, 125.7, 125.3, 124.2, 118.7, 18.9, 18 163.5, 152.4, 140.8, 140.6, 126.4, 124.9, 124.7, 124.5, 118.1, 21.0, 17.7, 12.2 6-Chloro-3-methyl-2H-chromen-2-one (3k) [11] Column chromatography on silica gel (ethyl acetate/ petroleum ether 1∶20) afforded the title product in 66% isolated yield as a white solid; 1 H NMR (400 MHz, CDCl 3 ) δ: 7.45 (s, 1H), 7.42-7.40 (m, 2H), 7.28-7.24 (m, 1H), 2.24 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ: 162.3, 152.3, 138.7, 131.1, 130.2, 128.0, 127.0, 121.4, 118.6, 21.0, 18.0 162.2, 154.1, 139.2, 136.9, 128.5, 126.6, 125.6, 118.8, 117.4, 17.9 161.3, 157.5, 138.6, 129.3, 126.1, 123.6, 121.4, 120.4, 118.4, 18 [16 ] Column chromatography on silica gel (ethyl acetate/ petroleum ether 1∶20) afforded the title product in 65% isolated yield as a white solid; 1 H NMR (400 MHz, CDCl 3 ) δ: 7.37 (s, 1H), 7.27-7.25 (m, 1H), 7.19 (d, J＝8.4 Hz, 1H), 2.42 (s, 3H), 2.39 (s, 3H), 2.21 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ: 163.0, 150.9, 146.7, 134.3, 132.1, 125.0, 122.9, 121.0, 117.2, 21.9, 15.8, 14.2 5,7-Dimethoxy-3,4,-dimethyl-2H-chromen-2-one (3o) [17] Column chromatography on silica gel (ethyl acetate/petroleum ether 1∶16 to 1∶8) afforded the title product in 62% isolated yield as a white solid; 1 H NMR 162.3, 159.4, 155.8, 149.3, 118.5, 106.3, 96.4, 93.8, 56.5, 56.4, 20.3, 13.8 3,4-Dimethyl-2-oxo-2H-chromen-7-yl acetate (3p) [17] Column chromatography on silica gel (ethyl acetate/petroleum ether 1∶16 to 1∶4) afforded the title product in 68% isolated yield as a white solid; 1 H NMR (400 MHz, CDCl 3 ) δ: 7.61 (d, J＝8.6 Hz, 1H), 7.10-7.05 (m, 2H), 2.41 (s, 3H), 2.35 (s, 3H), 2.23 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ: …”

Neoflavones. 2. Methods for Synthesizing and Modifying 4-Arylcoumarins

“…Condensing agents in this reaction include sulfuric [1, 2, 4, 7, 9, 11, 16, 18, 20-22, 24, 26-28, 30, 32, 33, 35, 36, 40, 44, 49, 52-55, 59, 60, 61, 63, 66-73], phosphoric [5,45], and trifluoroacetic acids [10], phosphoryl chloride in benzene [25], phosphorus pentoxide [34,36,37], boron trifluoride etherate [15,29,43], zinc chloride [1, 2,33], a solution of HCl in absolute ethanol [3, 6, 8, 11-13, 31, 38, 39, 41, 45, 47-50, 57, 58, 61, 62, 65, 69], and HF [19].…”

“…Phenols that have been used in the Pechmann condensation include resorcinol [1-15], 3-methylphenol [16,17], 4-methylphenol [18,19], 2,4-dimethylphenol [20], 3-methoxyphenol [7,21], 2-methylresorcinol [10,[22][23][24], orcine [10,14,25], 4-chlororesorcinol [10,26], 2-bromoresorcinol [27], 4-ethylresorcinol [28,29], β-resorcinolic acid methyl ester [30], 5-pentadecylresorcinol [31], 4-ethyl-2-acetylresorcinol [28], 2-methylhydroquinone [32], 2-ethylhydroquinone [32], pyrogallol [5,10,11,15,33,34,59,64], 4-ethylpyrogallol [35], pyrogallol-4-carboxylic acid ethyl ester [35], phloroglucinol [10,11,13 15,33,[36][37][38][39][40][41][42][43]…”

“…The structures of the products from condensation of o-hydroxyarylketones and anhydrides of the corresponding acids in the presence of base depend on many factors. The starting materials for synthesizing substituted 4-arylcoumarins 1 are o-hydroxybenzophenones of various structure and acetic anhydride in the presence of potassium or sodium acetates [34,37,58,[75][76][77][78][79][80][81][82][83][84][85][86][87][88][89][90][91][92][93][94].…”