An Improved Synthesis of (4-{4-Hydroxy-3-isopropyl-5-[(4-nitrophenyl)ethynyl]benzyl}-3,5-dimethylphenoxy)acetic Acid (NH-3)

Abstract

Sonogashira coupling of methyl {4-[3-iodo-5-isopropyl-4-(methoxymethoxy)benzyl]-3,5-dimethylphenoxy}acetate with (trimethylsilyl)acetylene afforded the corresponding (trimethylsilyl)ethynyl derivative in quantitative yield. Copper-free palladium-catalyzed coupling of this intermediate with 1-iodo-4-nitrobenzene afforded methyl (4-{3-isopropyl-4-(methoxymethoxy)-5-[(4-nitrophenyl)ethynyl]benzyl}-3,5-dimethylphenoxy)acetate in high yield. Saponification of the ester group, followed by the removal of the methoxymethyl group afforded (4-{4-hydroxy-3-isopropyl-5-[(4-nitrophenyl)ethynyl]benzyl}-3,5-dimethylphenoxy)acetic acid (NH-3).

Key words

coupling - Sonogashira coupling - palladium catalysis - 1-iodo-4-nitrobenzene - hydrolysis

References

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8

The spectral properties of the impurity were suggestive of a substituted benzofuran, but this was not verified.