Convenient two step synthesis of Si labelled tetraalkoxysilanes.

29Si enrichment would be advantageous for many NMR studies of the structural properties of sol-gel derived materials. The required starting materials (29Si enriched alkoxysilanes), however, are expensive and difficult to provide. Here we present a scalable, reliable synthesis of 29Si enriched tetraethoxysilane starting from silicon dioxide or elemental silicon with a total yield up to 75%.