Studies of quinones

Synthesis of Isoflavones by Tandem Demethylation and Ring-Opening/Cyclization of Methoxybenzoylbenzofurans

“…Another method that has been used to synthesize benzoyl­benzofurans devoid of substituents at C-2 is the conjugate addition of enamino­ketones to 1,4-benzoquinones. The latter method was employed in this study because it utilizes readily available starting acetophenones and benzoquinones and also affords the 3-benzoyl­benzofurans in a few steps and in good yields. − As shown in Scheme , the synthesis was initiated by reacting the TBDMS-protected acetophenone 8 with N,N -dimethylformamide dimethylacetal (DMF–DMA) followed by benzoquinone in HOAc. This gave the benzoylbenzofuran 9 in a low yield and the chromone 11 in a high yield .…”

“…The combined organic layer was washed with brine, dried over anhydrous MgSO 4 , and filtered, and the solvent was removed under vacuum. The residue was purified by silica gel flash column chromatography to afford the corresponding 3-benzoylbenzofuran. − …”

Microwave-Enhanced One-Pot Synthesis of Diversified 3-Acyl-5-Hydroxybenzofurans

“…3-Acyl-5-hydroxybenzofurans were first synthesized by Trofimov as early as 1967, by the condensation of pbenzoquinone with β-(dimethylamino)vinyl ketones that were prepared from methyl ketones and N,N-dimethylaminoformamide dimethyl acetal. 15 Initially, we employed this twostep sequence to synthesize 3-benzoyl-5-hydroxybenzofuran under conventional thermal heating for comparison purposes (Scheme 1). Step 1: the reaction of acetophenone 1a (R 1 ) Ph) with dimethylformamide dimethyl acetal 2a (R 2 ) H) was performed in refluxing DMF for 20 h to give intermediate enaminone 3a, which was unstable on silica gel but could be crystallized (yield 60-70%).…”

“…3-Acyl-5-hydroxybenzofurans were first synthesized by Trofimov as early as 1967, by the condensation of p -benzoquinone with β-(dimethylamino)vinyl ketones that were prepared from methyl ketones and N , N -dimethylaminoformamide dimethyl acetal . Initially, we employed this two-step sequence to synthesize 3-benzoyl-5-hydroxybenzofuran under conventional thermal heating for comparison purposes (Scheme ).…”