Synthesis, Molecular Structure, Conformational Analysis, and Chemical Properties of Silicon-Containing Derivatives of Quinolizidine

A silicon analog of quinolizidine 3,3,7,7-tetramethylhexahydro-1H-[1,4,2]­oxazasilino­[4,5-d]­[1,4,2]­oxazasilin-9a-yl)­methanol 3 was synthesized. X-ray diffraction analysis confirmed the trans configuration and low temperature NMR spectroscopy
both the flexibility (barrier of interconversion 5.8 kcal mol–1) and the conformational equilibrium (chair–chair
and chair–twist conformers) of the compound. The relative stability
of the different isomers/conformers of 3 was calculated
also at the MP2/6-311G­(d,p) level of theory. Intra- and intermolecular
hydrogen bonding in 3 and the appropriate equilibrium
between free and self-associated molecules was studied in solvents
of different polarity. Both the N-methyl quaternary ammonium salt
and the O-trimethylsilyl derivative of 3 could be obtained
and their structure determined.