A Practical Method for the Preparation of 1- and 2-(3-(Trimethoxysilyl)propyl)benzotriazoles

Carbofunctional trialkoxysilanes play an important role in materials chemistry, particularly as reagents for the covalent surface modification of inorganic oxide particles (SiO₂, TiO₂, etc.) and in sol-gel synthesis processes. They also serve as building blocks for the preparation of various organosilicon compounds, such as biologically active silatranes. Trialkoxysilanes bearing azolyl groups in the carbofunctional fragment are of particular interest. The availability of various azoles opens access to materials with tunable basicity, coordination properties, and reactivity, enabling the construction of complex functional moieties. Previously, we reported convenient preparative methods for the synthesis of 1-(3-(trimethoxysilyl)propyl)-1H-imidazole and 1-(3-(trimethoxysilyl)propyl)-1H-1,2,4-triazole. In the present work, this methodology has been extended to the corresponding benzotriazole derivatives.

We have demonstrated that 1- and 2-(3-(trimethoxysilyl)propyl)benzotriazoles can be readily obtained via a two-stage one-pot synthesis. The first stage involves the preparation of the sodium salt of benzotriazole by heating equimolar amounts of NaOH and benzotriazole in toluene with simultaneous azeotropic removal of the water formed. The second stage consists of alkylation with (3-chloropropyl)trimethoxysilane, which proceeds efficiently only in the presence of dimethylformamide upon refluxing the reaction mixture for 3 h. Using GC-MS and ¹H NMR spectroscopy, it was established that the reaction affords a mixture of 1- and 2-(3-(trimethoxysilyl)propyl)benzotriazoles in a 57:43 ratio, respectively, with an overall yield of 90%. Preparative separation of the isomers can be achieved by vacuum fractional distillation or flash chromatography on pre-dried silica.