2'-ACETOXY-2-HYDROXY-5-METHOXYBENZOPHENONE. PHOTOCHEMICAL SYNTHESIS, TRANSACYLATION AND CYCLIZATION TO 2-METHOXYXANTHONE

Article abstract of DOI:10.1016/0040-4020(82)80242-1

p-Methoxyphenyl salicylate 2 gives 2,2'-dihydroxy-5-methoxybenzophenone 3 upon irradiation, but the yields are low both in hexane and in methanol. p-Methoxyphenyl o-acetoxybenzoate 1 undergoes photo-Fries rearrangement, affording 2'-acetoxy-2-hydroxy-5-methoxybenzophenone 4 in good yield.Compound 4 is not stable in silica gel: it isomerizes to 2'-acetoxy-2-hydroxy-5'-methoxybenzophenone 5, that is also the major acetylation product of 3 with acetyl chloride.Starting from 1, 2-methoxyxanthone 7 is obtained in 57percent overall yield.