Aromatic phenol ether benzoylation

In general 3-benzylidenechroman-4-ones are prepared by condensation of chroman-4-ones with aromatic aldehydes (72). Strong alkaline (55) or acidic (75) conditions can be applied only if eventual sensitive substituents are suitably protected. Using dry hydrogen chloride in acetic acid Boehler and Tamm synthesized 5,7-di-O-methyleucomin (33) from 5,7-dimethoxychroman-4-one and anisaldehyde (9). Later Krishna-MURTY et al. (45) observed the simultaneous formation of a C-6 or C-8 a-chlorobenzylated product (34) in this reaction. Starting from O-benzoylated compounds 5,7-di-O-benzoyleucomin (35) and 4, 5,7-tri-0-benzoyl-4 -demethyleucomin (36) are easily prepared by this method using diethyl ether and ethyl acetate as solvents respectively (45). The unprotected phenolic compounds can be condensed successfully in boiling acetic anhydride (23, 24). The relatively low yield of 5,7-di-O-... 

The acetylation (with AC2O and HC104) and Vilsmeier formylation of sterically hindered phenols have been investigated. Substituted o-hydroxy-benzophenones have been prepared in 18-68% yields by treatment of the HMPT complexes of bromomagnesium phenoxides with aromatic aldehydes. " Phenolic O- vs. C-benzoylation has been studied, with particular reference to 3,4-disubstituted phenols. Previous work on the use of trifluoroacetic anhydride to promote aromatic acylation has been extended to the preparation of symmetrical and unsymmetrical benzophenones via reaction between the methyl and benzyl ethers of orcinol and the same ethers of phloroglucinolcarboxylic acid. " Other phenolic acylations include some chalcone syntheses and the acetylation and benzoylation of 2-hydroxy-4-methoxyacetophenone (peonol). ... 

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