Facile and convenient syntheses of quinones from phenols

Abstract

Two new highly effective and simple methods of oxidn. of dihydroxybenzenes and 2,6-disubstituted phenols lead to the corresponding quinones. The oxidn. is performed by hydrogen peroxide and catalyzed by halogens or hydrogen halides. The role of halogen catalysis is discusse

PPh3·HBr–DMSO: A Reagent System for Diverse Chemoselective Transformations

“…2b Prepared according to the general procedure discussed above: eluent, EtOAc/n-hexane (20%); isolated yield = 0.042 g, 85%; white solid; 1 2-Phenyl-4H-chromen-4-one (2f). 2b Prepared according to the general procedure discussed above: eluent, EtOAc/n-hexane (20%); isolated yield = 0.047 g, 95%; white solid; 1 H NMR (600 MHz, CDCl 3 ) δ = 8.24 (d,J = 7.8 Hz,1 H),2 H),1 H),4 H),1 H), 6.83−6.84 ppm (m, 1 H); 13 C NMR (150 MHz, CDCl 3 ) δ = 179. 5, 164.4, 157.3, 134.8, 132.8, 132.6, 130 1, 156.0, 153.7, 134.0, 126.4, 125.8, 123.1, 118.0, 110.6 ppm.…”

“…5c: EtOAc/n-hexane (3%); 0.008 g, 15%; yellow gum. 4c: 1 (d,J = 4.5 Hz,1 H),5.44 (d,J = 4.5 Hz,1 H), 2.10 ppm (s, 3 H); 13 C NMR (75 MHz, ) δ = 207.8, 140.0, 137.1, 134.4, 125.4, 124.5, 124.2, 123.0, 122.9, 75.3, 25.1 ppm; IR (KBr, cm −1 ) νÕ H = 3439, ν̃C O = 1717, ν̃m ax = 1428, 1356, 1102, 763, 735; HRMS (EI) m/z calcd for C 11 H 10 O 2 S [M] + : 206.0402; found: 206.0404. 5c: 1 H NMR (600 MHz, DMSO-d 6 ) δ = 9.01 (s, 1 H), 1 H),1 H),1 H),7.49 (td,J = 1.8,8.4 Hz,1 H), 2.49 ppm (s, 3 H); 13 C NMR (150 MHz,185.5,145.9,139.5,137.0,128.6,126.6,126.2,124.7,123.6,26.1 ppm;IR (KBr, ν̃C O = 1627, ν̃m ax = 1422, 1056, 750; HRMS (ESI) m/z calcd for C 11 H 8 O 2 SNa [M + Na] + 227.0143, found 227.0150.…”

“…5d: EtOAc/n-hexane (7%); 0.005 g, 9%; yellow solid; mp 65−67°C. 4d: 1 H NMR (300 MHz, CDCl 3 ) δ = 7.93 (d, J = 9.0 Hz, 2 H), 7.25− 7.27 (m, 2 H), 6.99−7.00 (m, 1 H), 6.90 (d, J = 8.7 Hz, 2 H), 6.02 (d,J = 6.6 Hz,1 H),4.47 (d,J = 6.6 Hz, 1 H), 3.85 ppm (s, 3 H); 13 C NMR (75 MHz,CDCl 3 ) δ = 196.7,164.2,140.3,131.5 (2 CH),126.7,126.3,123.8,114.0 (2 CH), 70.9, 55.5 ppm; IR (KBr, cm −1 ) ν̃O H = 3443, ν̃C O = 1667, νC C = 1603, νm ax = 1266, 1231, 1192, 1091HRMS (ESI) J = 3.0,9.0 Hz,2 H),7.66 (dd,J = 1.2,5.4 Hz,1 H),7.39 (dd,J = 3.0,5.4 Hz,1 H),6.98 (dt,J = 3.0,9.0 Hz, 2 H), 3.89 ppm (s, 3 H); 13 C NMR (150 MHz,CDCl 3 ) δ = 192.9,188.7,166.0,139.3,137.9,133.6 (2 CH),128.2,128.0,126.7,115.3 (2 CH), 56.6 ppm; IR (KBr, cm −1 ) ν̃C O = 1651, ν̃C C = 1601, ν̃m ax = 1508, 1166, 1262, 1232, 834, 738, 609; HRMS (ESI) m/z calcd for C 13 H 10 O 3 SNa [M + Na] + 269.0249, found 269.0247.…”

Vanadium-substituted Keggin heteropolycompounds as catalysts for ecofriendly liquid phase oxidation of 2,6-dimethylphenol to 2,6-dimethyl-1,4-benzoquinone

“…Several researchers have utilized H 2 O 2 as oxidant in the synthesis of p-benzoquinones. Minisci et al [10] have reported the oxidation of dihydroxybenzenes by H 2 O 2 in methanolic or aqueous solution of H 2 SO 4 , at room temperature in the presence of I 2 or HI as catalysts. A similar procedure has been utilized for the synthesis of p-quinones from 2,6-disubstituted phenols with high yields and selectivity, so this procedure is recommended as a valuable method also for industrial applications.…”

Photocatalytic degradation of 1,4-benzoquinone in aqueous ZnO dispersions

“…The identification of hydroquinone does not contradict the usual order of formation of intermediates proposed by many authors (phenols, hydroquinones, benzoquinones, carboxylic acids then CO 2 and H 2 O respectively), because the formation of hydroquinone from benzoquinone is a reversible process. 30,31 Mineralisation is the main aim of the photodegradation of 1,4-BQ and this can be followed by measuring the total organic carbon.…”