In Situ Monitoring of Allylamine and 1,1,3,3-Tetramethyldisiloxane Reaction to Form 2,2,7,7-Tetramethyl-1-oxa-3-aza-2,7-disilacycloheptane Using Raman Spectroscopy

Abstract

The cyclic siloxazane, i.e., 2,2,7,7-tetramethyl-1-oxa-3-aza-2,7-disilacycloheptane (1), is a useful industrial intermediate that is challenging to produce. One method to synthesize 1 is through concurrent dehydrocoupling and hydrosilylation reactions between 1 and allylamine. This chemistry is highly exothermic and also generates a significant amount of H2. Raman spectroscopy was demonstrated to be an effective analytical method to track both reactions. It enables a safe reaction scale-up by monitoring the consumption of allyl groups and the silicon hydride (SiH) groups. Both functional groups could be readily quantified by using a solvent as an internal standard. It is found that the observed SiH signal can be attributed to an intermediate species, which would undergo a relatively slower hydrosilylation reaction. Interesting kinetics behavior is observed that leads to a mechanistic understanding of the catalyst's role in catalyzing the two elementary steps. The ability to track these moieties is critical to the development of a safe process that avoids accumulation of SiH intermediates.