Alumina-Catalyzed Reactions of Hydroxyarenes and Hydroaromatic Ketones. 10. Reaction of Phenol with 2-Propanol

Article abstract of DOI:10.1021/jo01310a013

At 300-350 deg C in the presence of alumina, phenol (1) reacts with excess 2-propanol (37) to give mixed monopropyl-, dipropyl-, and 2,4,6-triisopropyl- (42) phenols. At 300 deg C the principal components of the product mixture are 2-isopropylphenol (26-30 mol percent yield) and 2,6-diisopropylphenol (44-52percent); at 350-400 deg C , they are the isomeric monoisopropylphenols (50-60percent). With 3-isopropylphenol as substrate (instead of 1), 2,5-diisopropylphenol is obtained (79percent), while 4-isopropylphenol gives 2,4-diisopropylphenol and 42 (70percent combined yield). In various runs, 0-20percent of the propyl groups introduced are n-propyl ones. It is proposed that the principal products result from an S_N2-type reaction mechanism which involves nucleophilic attack (variously by C-2, C-4, and C-6) of an adsorbed ambident phenoxide ion onto C-2 of an adsorbed isopropoxide group. n-Propylation is ascribed to a side reaction of S_N1 type.