ChemInform Abstract: A New One‐Step Synthesis of 3‐Aryl‐4‐hydroxycoumarins.

Synthesis of Coumarins, 4-Hydroxycoumarins, and 4-Hydroxyquinolinones by Tellurium-Triggered Cyclizations1

“…Variations of the Dieckmann cyclization have been applied to the synthesis of 5a and 5d . Treatment of the methyl ester of 2-propionyloxybenzoic acid with sodium at elevated temperatures 37a,b or with sodium hydride 37c gave 5a in yields of 71%, 28%, and 30−40%, respectively …”

“…Likewise, the methyl ester of 2-phenylacetoxybenzoic acid gave 5d on treatment with sodium (25%),37b dry potassium carbonate (85%),37d or potassium hydroxide in pyridine (40−60%) 37e. Coumarins 5b and 5c have not been prepared by cyclization involving 3−4 bond formation.…”

“…Coumarins 5b and 5c have not been prepared by cyclization involving 3−4 bond formation. The former has been obtained in 52% yield from 5-methyl-2-hydroxypropiophenone, dry potassium carbonate, and carbon dioxide (40 atm, 170 °C),37f and the latter in 4% yield from 1,4-dimethoxybenzene and methylmalonyl chloride catalyzed by aluminum chloride …”

“…Coumarins (2 H -1-benzopyran-2-ones) have been prepared by a number of methods involving formation of a 3−4 carbon−carbon bond . For example, the Kostanecki−Robinson reaction of o -hydroxyarylalkyl ketones with an acid anhydride and the sodium salt of an acid produces coumarins by formation of the 3−4 carbon−carbon bond via the ester enolate, but chromones (4 H -1-benzopyran-4-ones) can be the major products via the ketone enolate, and yields can be variable. , A method (Claisen) that avoids the chromone byproducts of the Kostanecki−Robinson reaction is the treatment of methyl esters of 2-alkanoyloxybenzoic acids with metallic sodium 37a,b or with bases. 37c-f Coumarins also have been prepared in good yields by a ring-closing metathesis reaction (3−4 bond formation), but this reaction is not ideal with respect to carbon atom economy and requires a ruthenium catalyst.…”

Antagonists of Vitamin K—Popular Coumarin Drugs and New Synthetic and Natural Coumarin Derivatives

“…For example, the Kostanecki-Robinson reaction of o-hydroxyarylalkyl ketones with an acid anhydride and the sodium salt of an acid produces coumarins by the formation of the 3-4 carbon-carbon bond after enolization of the ester (this step is marked by the red rectangular in Scheme 4), but chromones (4H-1-benzopyran-4-ones) can be the major products via the ketone enolate, and yields can be variable [82][83][84][85][86]. A method that avoids the chromone byproducts of the Kostanecki-Robinson reaction is based on the treatment of methyl ester of 2-alkanoyloxybenzoic acids with metallic sodium [87,88] or bases [89][90][91][92]. Coumarins also have been prepared in good yields by a ring-closing metathesis reaction (3-4 bond formation) [93,94] but this reaction is not ideal in respect to the carbon atom economy and requires a ruthenium catalyst.…”