Facile Transfer Hydrogenation of Chromones

Abstract

Refluxing a solution of chromones in methanol containing ammonium formate and Pd-C leads to facile hydrogenation to chromanones.

Stereoselective synthesis of cis-2-(polyfluoroalkyl)chroman-4-ols and trans-4-acylamino-2-(polyfluoroalkyl)chromans

“…15 We found that 2-R F -chromones 1a-c smoothly reacted with sodium borohydride in methanol to afford cis-2-(polyfluoroalkyl)chroman-4-ols 2a-c in good yields (65-83%). The corresponding chromanone 3, intermediate of the reaction, is in situ reduced to chromanol 2 because the reduction of 3 is faster than that of 1 due to double bond conjugation in the latter.…”

Synthesis and some properties of 2-(polyfluoroalkyl)chroman-4-ols and 2-(polyfluoroalkyl)chroman-4-ones

“…11 The selective reduction of the С=С bond in chromones and flavones was carried out only under the action of diisobutylaluminium hydride 12 and the HCO 2 NH 4 /Pd-C system in methanol. 13 We found that 2 R F chromones 1a-e, obtained by the condensation of 2 hydroxy and 2 hydroxy 4 methoxy acetophenones with ethyl polyfluoroalkanoates, 14 are readily reduced by NaBH 4 in methanol to 2 R F chroman 4 ols 2a-e (5-20 °C, 0.5 h, 65-90% yields). For loads of chromone 1a higher than 0.2 mole, the reaction was carried out in ethanol first at 5-20 °C and then on heat ing (Experimental).…”

Synthesis of O-methyl epi-heliannuol E

“…We have recently generalised this as a useful protocol for the reduction of chromones to chromanones. 12 Subsequently it was also found that carefully controlled (monitored by TLC) catalytic hydrogenation of 9 in the presence of Pd -C (10%) results in smooth reduction of the double bond and also the ketone to produce the corresponding chromanol, which could be efficiently oxidised by Jones reagent to the benzopyranone carboxylate 10 in good overall yield.…”

“…3.1.6. 2-(1-Hydroxy-1-methyl)-ethyl-4,4-dithioethane-6-methoxy-7-methyl-2H-1-benzopyran (12). To a magnetically stirred solution of MeMgI [prepared from Mg (120 mg, 5 mmol), MeI (850 mg, 6 mmol)] in ether (5 mL) at 08C was added a solution of the thioketal 11 (680 mg, 2 mmol) in ether (4 mL).…”