Prodn. of bis-(2-hydroxyphenyl-3 (2H)-benzotriazole) methane derivs. - by reacting benzotriazole(s) with para:formaldehyde or trioxane in homogeneous soln. in conc.sulphuric acid

摘要

Prodn. of bis-(30((2H)-benzotriazol-2-yl) -2-hydroxy-phenyl)methane derivs. (I) is carried out by reacting 2-hydroxy-phenyl- 2H-benzotriazoles (II) with paraformaldehyde (IIIA) or 1,3,5-trioxane (IIIB) in homogeneous soln. in conc. H2SO4 at 0-60 deg. C, with a (II):(III) molar ratio of 2.0:(1.0-1.5). R1 = 1-6C alkyl or 6-10 C aryl; R2 = H or halogen. The reaction temp. is pref. 5-40, esp. 10-35 deg. C. USE/ADVANTAGE - (I) are useful as UV absorbers for plastics and photographic films. The process is esp. useful for producing readily soluble (I) which are difficult to crystallise, i.e. (I) with the above substits.. The reaction is exothermic, avoiding the need for additional heating, and takes only 2-8 h.. Only one stage is involved and the yield and prod. colour are much better than in some conventional methods.