A novel phosgene-free route to different isocyanates starts from CO 2 and aminosilanes (cf. silylamines) to form so-called carbamoyloxysilanes (O-silylcarbamates), i. e., compounds with the general motif R 1 R 2 NÀ COÀ OÀ SiR 3 R 4 R 5 as potential precursors. We focused on the insertion reaction of CO 2 into SiÀ N bonds of substrates with cyclic (mostly aromatic) amine substituents, i. e.

New cyclic and spirocyclic aminosilanes were synthesised using ethylenediamine, 2-aminobenzylamine, 1,8-diaminonaphthalene, o-phenylenediamine, and trans-cyclohexane-1,2-diamine as starting material. These diamines were converted into aminosilanes using silicon tetrachloride and dimethyldichlorosilane directly and via the N,N’-bis(trimethylsilylated) amino derivatives. 15 new compounds of the type (diamino)(SiMe3)2, (diamino)2Si, (diamino)SiMe2, and (diamino)SiCl2 have been prepared. The formation of two cyclotrisilazane derivatives was observed starting from (N,N’-2-aminobenzylamino)dichlorosilane by trimerisation. All synthesised compounds have been characterised with NMR-, Raman-, or IR-spectroscopy, mass-spectrometry, and boiling or melting point. Single-crystal X-ray structure analyses of several derivatives have been performed. The degree of substitution with trimethylsilyl groups in the final compounds depends on the ring size of the spirocycles. It was shown with quantum chemical calculations on the M062X/6-31G(d) level that trimethylsilyl groups have a stabilising effect on 5-membered ring systems and a destabilising effect on 6-membered rings in these compounds.