Neutral alkoxysilanes from silica gel and N-phenyldiethanolamine

We report the preparation of a mixture of alkoxysilanes using silica gel and the dialcohol N-phenyldiethanolamine as starting materials, through a low-energy oxide one-pot synthesis (OOPS). We carried out a detailed study of reaction conditions, which revealed that it is possible to dissolve 94% of silica gel in the presence of KOH as catalyst in 60 min, a result in marked contrast with other polyalcohol–silica gel reacting systems, where dissolved silica yields are lower and reaction times are longer. According to 29Si NMR studies, the product obtained is a mixture of several tetracoordinated silicates that includes tetraalkoxysilanes and trialkoxydisiloxanes dissolved in an excess of the ligand. From this mixture, it is possible to isolate and fully characterize the complex Si[(OCH2CH2)2NPh]2, 1, which is the main product, and this compound can be functionalized to give the complex Si[(OCH2CH2)2NPh(p-Br)]2, 2, broadening the scope of the chemistry possible with these alkoxysilanes.

Graphical abstractSilica gel is dissolved by the dialcohol N-phenyldiethanolamine through a low-energy oxide one-pot synthesis (OOPS) yielding a mixture of several tetracoordinated silicates that includes tetraalkoxysilanes and trialkoxydisiloxanes dissolved in an excess of the ligand. From this mixture, it is possible to isolate and fully characterize the main product Si[(OCH2CH2)2NPh]2, 1.Figure optionsDownload full-size imageDownload as PowerPoint slide