O-hydroxyaryl ketones

The method has been extended to o-hydroxyaryl ketones for the synthesis of naphtho[l,2-6]furanes,656 thieno[3,2-e]benzofurans,657 furo-flavones,658 furoxanthones,659 furoquinolines,611,660 phenanthrofur-ans,660 and other complex benzofurans.661... 

Treatment of acylhydrazones of o-hydroxyaryl ketones with LTA in THF at room temperature results in smooth, very high yield conversion into 1,2-diacylbenzenes, e.g. 1 — 2. The mechanism of this very unusual replacement of a phenolic OH group by an acyl group has been studied in detail, and standard crossover experiments using, for example, a mixture of 1 and its 3,5-dibromo derivative established that the process was intramolecular. Use of 1 in which the oxygen atom of the benzoyl group was labelled as 180 gave exclusively the labelled product 3. 

Kostanecki SV, Rozycki A (1901) Formation of chromones or coumarins by acylation of o-hydroxyaryl ketones. Ber 34 102... 

Salicylaldehydes and some o-hydroxyaryl ketones react with Meldrum s acid to give coumarin-3-carboxylic acids <03TL1755>. 3-Cyanocoumarins, and thus the 3-carboxylic acids, are available in high yield from a Knoevenagel reaction between salicylaldehydes and malononitrile in water <0382331>. 3-Chlorocoumarins result from the cathodic reduction of trichloroacetyl esters of o-hydroxyacetophenones <03T9161>. 

Allan-Robinson reaction. Preparation of fla-vones or isoflavones by condensing o-hydroxyaryl ketones with anhydrides of aromatic acids and their sodium salts. 

Kostanecki acylation. Formation of chro-mones or coumarines by acylation of o-hydroxyaryl ketones with aliphatic acid anhydrides followed by cyclization. 

Synthesis of 4-chromanones by condensation of salicylaldehydes or o-hydroxyaryl ketones with enamines or ketones (see 1 st edition). 

Synthesis of 4-chremanones by condensation of salfcylaldehydes or o-hydroxyaryl ketones... 

Cleavage of azones. The regeneration of ketones from semicarbazones and to-sylhydrazones is rapid and high yielding. It is jerformed at room temperature in aqueous MeCN. The acylhydrazones of o-hydroxyaryl ketones are transformed into 1,2-diacylbenzenes. ... 

This reaction was first reported by Allan and Robinson in 1924. It is the synthesis of fiavones or isoflavones derivatives by means of the condensation between o-hydroxyaryl ketones and an anhydride of aromatic acid in the presence of the sodium salt of corresponding acid in the anhydride. Thus this reaction is known as the Allan-Robinson condensation, Allan-Robinson s flavone synthesis, Allan-Robinson reaction, and Allan-Robinson synthesis. ... 

Synthesis of flavones or isoflavones by the treatment of of o-hydroxyaryl ketones with aromatic aldehydes. Cf. Kostanecki reaction on page 322. 

Upon boiling colupulone in methanol hydrogen chloride 12 N 10 3 during 3.5 h, two crystalline derivatives with molecular formula C20H28O4 s " obtained (1,2). The compound with a melting point of 83°C (190, Figs. 107 and 113) is synthesized by reaction of phlorisobutyrophenone with two equivalents of 3-methyl-2-butenyl bromide in dry chloroform (3). The neutral character of the tricyclic molecule is ascribed to the presence of an o.-hydroxyaryl ketone (4,5). Compound 190 can also be prepared by... 

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