Abstract
Fries rearrangement of phenyl 1, ο-tolyl 2, m-tolyl 3 and ρ-tolyl diphenylacetates 4carried out in nitrobenzene with anhydrous aluminium chloride (AlCl3) at 60°C, gave diff erent yields and ortho/para ratios of the corresponding products hydroxyphenyl ketones, d epending upon the position of a methyl substituent on the phenyl ring. The rate of the reactions is in the order of 1>2>4>3, and the highest ortho/para ratio was observed for 3(Table 1, Fig.1 and Fig.2). The reaction of these aryl diphenylacetates was compared with the rearrangement of phenyl 5, ο-tolyl 6, m-tolyl 7 and ρ-tolyl 8; The yield and ortho/para ratio were higher than those of phenyl diphenylmethyl ketones with an exception of a large ortho/para ratio for 7 (Table 2). In the rearrangement of 1, 5 and phenyl triphenylacetate 9, the reaction rate and orthof para ratio were in the order of 5>1>9. Each acyl cation derived from 1, 5 and 9 (PhCH2C=O, Ph2CHC=O and Ph3C=O) is understood to be effective electrophiles (Table 4). In the crossover reaction of 1, 5 and 9with toluene, the corresponding ρ-tolyl ketones were formed in moderate yields together with small amounts of ρ-hydroxyphenyl ketones (Table 3), including that 1 and 5 proceeded in both inter- and intramolecular pathways, while 9 is an intramolecular migration pathway. In order to examine possible reverse Fries rearrangement, the rearrangement products 10, 11, 12, 13, 14 and 15 were treated with AlC13 in nitrobenzene (Table 5). The formation of 1 and 2 indicated the reverse Fries rearrangement of 10 and 12, respectively, and a rearrangement from 11 to 1 and an isomerization from 11 to 10 were detected as seemingly slow processes. Compound 13 was recovered almost quantitatively. Compounds 14 and 15were found interconversible under these conditions.
