Uvistat-L,Ward Blenkinsop,UK,1960
2-Hydroxy-4-methoxy-4'-methyl-benzophenone is an UV absorbing agent in sunscreen cosmetic creams, lotions, lipstieks, sun oils, etc.
Preparation by Friedel–Crafts acylation of m-methoxy-phenol with p-toluoyl chloride,
in the presence of boron trichloride in benzene first at ?10°, then at reflux for 10 h under nitrogen (80%)
in the presence of titanium tetrachloride in benzene first at ?10°, then at reflux for 14 h under nitrogen (73%) or in chlorobenzene for 1 h at 120° (79%).
ChEBI: Mexenone is a member of benzophenones.
p-Toluoyl chloride is the starting material. To this is added chlorobenzene and
1,3-dimethoxybenzene. The reaction mixture is cooled to 12°C in an ice bath
and aluminum chloride is added gradually, keeping the reaction below 30°C.
The reaction is then gradually heated to 115°C with the evolution of hydrogen
chloride gas. As the temperature increases, the reaction mixture becomes
thicker. At 105°C, dimethyl formamide is added slowly. The reaction is heated
at 115°C for a short time and is then poured into concentrated hydrochloric acid. The reaction mixture pours very easily and very cleanly. The acid
mixture is heated with steam to dissolve all the material which had not
hydrolyzed and the mixture is filtered. The red chlorobenzene layer is
separated and washed twice with hot water.
To the chlorobenzene solution is then added sodium hydroxide dissolved in
water and the chlorobenzene is removed by a steam distillation. After all of
the chlorobenzene is removed, the precipitate which forms during the
distillation is removed by filtration and discarded. The solution is cooled and
acidified with hydrochloric acid, precipitating a tan solid. This is removed by
filtration and washed acid-free. It is then treated with sodium bicarbonate
solution to remove any acid present and is then washed with water to remove
all traces of bicarbonate. After drying approximately a 75% yield of mexenone
is obtained.
BZP-10 is exceptionally positive in ketoprofen-photosensitive
patients.
