Acylation of Multiple Anions of Poly-β-ketones by Hydroxy- and Alkoxybenzoates. Cyclization of the Resultant Tetraketones to Benzophenones and Xanthones

Article abstract of DOI:10.1021/jo00324a012

The dianion (2) of 2,4-pentanedione and the trianion (10) of 2,4,6-heptanetrione were acylated by lithium salts of the unprotected hydroxybenzoates methyl 2-hydroxy-4-methoxy-6-methylbenzoate (1b), methyl 2,6-dihydroxy-4-methoxybenzoate (7b), and methyl 2,4-dimethoxy-6-hydroxybenzoate (7c), as well as by the alkoxybenzoates methyl 2,4,6-trimethoxybenzoate (7d) and methyl 2,4,6-tribenzoxybenzoate (7e).The aryl 1,3,5,7-octanetetraones (11b-d and 12) resulting from acylation of 10 were cyclized in biomimetic processes to naturally occurring benzophenones and xanthones.Hydrogenolysis of 1-(2,4,6-tribenzoxyphenyl)-1,3,5,7-octanetetraone (11e) and cyclization gave norlichexanthone (20).