ChemInform Abstract: Novel Method in Synthesis of 3‐Phenyl‐4‐styryl‐ and 3‐Phenyl‐4‐hydroxycoumarins. Formation of Benzisoxazole‐3‐phenylacetic Acid from 3‐Phenyl‐4‐hydroxycoumarin and NH2OH·HCl.

Abstract

The coumarins (IV) and (VII) mentioned in the title are prepared by the esterification of phenylacetic acid (II) with the hydroxybenzenes (I) or (V) and subsequent cyclization of the esters (III) and (VI) respectively.

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.…”