Abstract
It was found that the ethoxycarbonyl derivative (2) of salicylic acid (1) was reduced to o-cresol (3) with sodium borohydride in good yield and the best reaction conditions were the use of 4 molar equivalents of sodium borohydride in tetrahydrofuran-H2O at 5-15.°p-Hydroxybenzoic acid (4) and m-hydroxybenzoic acid (6) did not give the corresponding cresols in this procedure, and o-hydroxyphenylacetic acid (8) did not give o-ethylphenol. These results show that the existence of o-hydroxy group is necessary to reduce the carboxyl groups to the methyl groups and only the carboxyl groups which are directly attached to aromatic nuclei are reduced to the methyl groups. Several o-hydroxybenzoic or -naphthoic acids (1, 10, 12, 15, 17, 19 and 24) were reduced to the corresponding o-methylphenols in good yields. It was found that all hydrogen atoms of the methyl group were introduced from sodium borohydride.
