Baker-Venkataraman synthesis

Baker-Venkataraman synthesis, 2, 76 Balsoxin, 6, 232 Bamicetin isolation, 3, 147 Band theory semiconductors, 1, 355 Ban thine... 

A facile Baker-Venkataraman synthesis of flavones (39), using PTC, has been recently proposed by Jain et al.66... 

BAKER VENKATARAMAN Flavone synthesis Rearrangement of aromatic keto esters ot phenols to tiavones... 

Method 1 is a new method for the direct production of flavone from o-benzoyloxyacetophenone and has been successfully applied to the synthesis of other flavones. Method 2, which involves the Baker-Venkataraman transformation, is recommended because of its high over-all yield and the reproducibility of the results. Mozingo and Adkins method 8 is satisfactory but the yield of 0-hydroxydibenzoylmethane is variable. 

It has since been shown that the enol ester (451) is an intermediate in the synthesis (69T715). Indeed such esters readily form chromones on treatment with alkali and the ortho acyloxy group becomes part of the pyranone ring as a result of a Baker-Venkataraman rearrangement (Scheme 160) (69T707). 

The value of l-(o-hydroxyphenyl)-3-arylpropane-l,3-diones in the synthesis of O-heterocycles by the Baker-Venkataraman reaction with aroyl chlorides has been exemplified by their conversion into 3-acylflavones, flavones, flavanones and... 

There is much interest in anthrapyran antibiotics. Synthesis of S-indomycinone indicates that a revision is required <07CEJ9939>. A total synthesis of racemic y-indomycinone 49 based on a Baker-Venkataraman rearrangement of the anthraquinone ester 47 and cyclisation of the resulting diketone to the chromone 48 has been reported <07EJ01905>. A total synthesis of the structurally simpler topopyrone C involves similar methodology <07TL1049>. In an alternative approach which is readily adaptable to the synthesis of other anthrapyrans, the... 

BAKER - VENKATARAMAN Flavone synthesis Rearrangement 0/ aromatic keto esters ol phenols to Navones... 

BAER FISCHER Ammo sugar synthesis 10 BAEYER Oxindolesynthesis It BAEYER Oiarylmethane synthesis 11 BAEYER Pyridine synthesis 12 BAEYER - DREWSON Indoxyt synthesis 12 BAEYER VILLIGER Ketone oxidation 13 BAEYER - VILLIGER Tntylation 13 BAKER - VENKATARAMAN Flavone synthesis t4... 

The base-catalyzed rearrangement of aromatic ort/70-acyloxyketones to the corresponding aromatic (3-diketones is known as the Baker-Venkataraman rearrangement. 3-Diketones are important synthetic intermediates, and they are widely used for the synthesis of chromones, flavones, isoflavones, and coumarins. The most commonly used bases are the following KOH, potassium fert-butoxide in DMSO, Na metal in toluene, sodium or potassium hydride, pyridine, and triphenylmethylsodium. 

In the laboratory of K. Krohn, the total synthesis of akianonic acid and its derivatives was undertaken, utilizing the Baker-Venkataraman rearrangement of ort/70-acetyl anthraquinone esters in the presence of lithium hydride. Using this method, it was possible to introduce ketide side-chains on anthraquinones in a facile manner. 

V. Snieckus and co-workers developed a new carbamoyl Baker-Venkataraman rearrangement, which allowed a general synthesis of substituted 4-hydroxycoumarins in moderate to good overall yields. The intermediate arylketones were efficiently prepared from arylcarbamates via directed ortho metallation and Negishi cross coupling. The overall sequence provided a regiospecific anionic Friedel-Crafts complement for the construction of ortho-acyl phenols and coumarins. 

Stigmatellin A is a powerful inhibitor of electron transport in mitochondria and chloroplasts. During the diastereo- and enantioselective total synthesis of this important natural product, D. Enders et al. utilized the Baker-Venkataraman rearrangement for the construction of the chromone system in good yield. ... 

A highly efficient and operationally simple domino reaction was developed in the laboratory of S. Ruchiwarat for the synthesis of benz[h]indeno[2,1-e]pyran-10,11-diones. The initial aroyl-transfer was achieved by the Baker-Venkataraman rearrangement by subjecting the starting material to KOH in pyridine under reflux for 30 minutes. 

Rao, A. V. S., Rao, N. V. S. Synthesis of some substituted 2-(2-furyl)chromones by the simplified Baker-Venkataraman transformation. 

Makrandi, J. K., Kumari, V. A convenient synthesis of 2-styrylchromones by modified Baker-Venkataraman transformation using phase transfer catalysis. Synth. Common. 1989, 19, 1919-1922. 

Song, G.-Y., Ahn, B.-Z. Synthesis of dibenzoylmethanes as intermediates for flavone synthesis by a modified Baker-Venkataraman rearrangement. Arch. Pharm. Res. 1994, 17, 434 37. 

Kalinin, A. V., Snieckus, V. 4,6-Dimethoxy-3,7-dimethylcoumarin from Colchicum decaisnei. Total synthesis by carbamoyl Baker-Venkataraman rearrangement and structural revision to isoeugenetin methyl ether. Tetrahedron Lett. 1998, 39, 4999-5002. 

Krohn, K., Roemer, E., Top, M. Total synthesis of akianonic acid and derivatives by Baker-Venkataraman rearrangement. Liebigs Ann. Chem. 1996, 271-277. 

Thasana, N., Ruchirawat, S. The application of the Baker-Venkataraman rearrangement to the synthesis of benz[b]indeno[2,1-e]pyran-10,11-dione. Tetrahedron Lett. 2002, 43, 4515-4517. 

There are scanty reports about the Baker-Venkataraman rearrangement which is used in synthesis very seldom. Thus, in the approach mentioned in equation 106 the C-glycoside 239 undergo O-benzoylation to afford the ester 240, which rearranges into the 1,3-dicarbonyl compound 241 formed as a keto-enol mixture in 48% yield (equation 109) ° . 

Claisen condensation between an ester and the methylene adjacent to the carbonyl of the acylarene produces a l-(ortft(9-hydroxyaryl)-l,3-diketone. The Claisen condensation can be conducted in the presence of the acidic phenolic hydroxyl by the use of excess strong base triethylamine as solvent and base can also be utilised. " Alternatively, the process is conducted in two steps first, acylation of the phenolic hydroxyl, and secondly, an intramolecular ° base-catalysed Claisen condensation, known as the Baker-Venkataraman rearrangement a synthesis of flavone itself is illustrative. ... 

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