Benzo furan-4,7-dione

Diels-Alder reactions of benzo[i)]furan-4,5-diones and benzo[ )]furan-4,7-diones 99H(50)1137. 

Benzo[b]furan-4,7-dione, 6-methoxy-2-methyl-(acamelin)... 

Benzo[c]furan-4,7-dione, l-(2-hydroxy-6-methoxyphenyl)-5-methyl-X-ray, 4, 540 <80JCS(P1)2447> Benzo[c]furan-l(3H)-one, 5-methyl-4,7-dimethoxy-... 

Nebois P., Pillion H. Diels-Alder Reactions of Benzo[h Furan-4,5-Diones and Benzo[h Fnran-4,7-Diones Heterocydes 1999 50 1137 1156... 

Diels-Alder reactions of benzo[fc]furan-43-diones and benzo[b]furan-4,7-diones have been reported <99H(50)1137>. The activation of a C-0 bond in a Mn(C0>3 complexed benzo[i>]furan was examined <99AG2343>. The enzyme-catalyzed dealkylation of (+)-marmesin to the phototoxic psoralene (and acetone) has been investigated <99AG413>. A hi yielding synthesis of bidentate bisoxazoline DBFOX/Ph [(R,R)-4,6-dibenzofutandiyl-2 2 -bis(4-phenyloxazoline)] was developed. DBFOX/Ph was subsequently tested in enantio-selective conjugate radical additions onto 3-(3-phenyl-2-propenoyl)-2-oxazolidinone <99TA2417>. 

As described in Section IV,C, benzo[c]furans react with o-quinones to give [4 + 4]-adducts and/or dioxoles. The same products are obtained when higher o-quinones such as 9,10-phenanthrenequinone (263), bcn/o[A]-quinoline-5,6-dione (264) and 5,6-chrysenequinone (265) are irradiated with benzo[c]furans (Scheme 17) % the dioxoles may react with a further molecule of excited 263 to give 2 1 adducts (273). 

Benzo[c]furan-4,7-diones were probably synthesized for the first time by Pummerer and co-workers. Condensation of benzoin and hydro-... 

The syntheses leading to carbocyclic hydrogenated derivatives of benzo[6]furans are based mainly on the ring closure of 1,4-diketones, e.g. 2-acetonylcyclohexane-l,3-dione gives 6,7-dihydro-4(5if)- benzofuranone. 

A series of dibenzofuran-l,4-diones illustrated in the following scheme were constructed via a DDQ-mediated intramolecular oxidative cyclization of quinone-arenols <070L2807>. Dibenzo[b] furans were also found to be made from 2//-pyran-2-ones and 6,7-dihydro-577-benzo[Z>]furan-4-one <07T1610>. The asymmetric synthesis of chiral furo-fused BINOL derivatives was achieved via copper(II)-mediated oxidative coupling from naphthofuranol in the presence of chiral phenylethylamine <07TL317>. 

The oxidative formation of the quinone part was used also for the preparation of some benzo[h]naphtho[2,3-d]furan-6,l 1-diones [brasanquinones (137)] (03CB2199,03CB2202 08CB2373 09JCS398 70JIC567) or analogous systems (78CJC517). 

In the furoquinone series, a new compound, isotanshinone, was isolated. The compound has a benzo analog skeleton of 84 (87MI7). The preparation of 3-methylbenzofuran-4,5-dione is described and its dienophilicity was studied (87TL3427). A direct synthesis of some heterocyclic quinones is reported. The method is a direct one-step ortho-bisacylation of hydroquinones under very mild conditions and in the presence of AICI3. Examples of acylation with furan-3,4- and pyridine-3,4-dicarboxylic acid dichlorides are described (87TL1533). 

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