Persistent Dialkylsilanone Generated by Dehydrobromination of Dialkylbromosilanol

A persistent dialkylsilanone was synthesized by the dehydrobromination of a dialkylbromosilanol with tris(trimethylsilyl)silyl potassium in solution at ?80 °C: It was characterized by NMR and IR spectroscopy, and was tested in several reactions. In ²⁹Si NMR spectrum in [D₈]toluene, the signal due to the unsaturated silicon nuclei was observed at 128.7 ppm. Reactions of the dialkylsilanone with water and mesitonitrile oxide gave a silanediol and a [2+3] cycloadduct, respectively. The silanone remains intact in [D₈]toluene below ?80 °C for at least two days, while it undergoes unprecedented isomerization to give a siloxysilene by means of 1,3‐silyl migration at higher temperatures.     

Cover Picture: Chem. Eur. J. 2/2003

The cover picture conveys the concise message that a fixed element of axial chirality residing in one ring of a catenane can induce chirality of a helical nature within a dynamic setting in the other (interlocked) ring. The overwhelming preference for one enantiomeric pair within a bipartite set of diastereoisomers relating to the particular [2]catenane, presented as its X‐ray crystal structure in the circular inset, becomes more and more pronounced as its 1,4‐dioxybenzene units are replaced, one at a time, by 1,5‐dioxynaphthalene ones, with their concomitant planar chiralities. The very high levels of induction of dynamic helical and planar chiralities by a fixed source of axial chirality in a simple catenane conjures up a number of scenarios where this approximately cubic nanometer of programmable information might be put to good use. For more details concerning these tiny stereochemical wonders with no stereogenic center in sight, see the article on p. 543 ff by J. F. Stoddart and D. J. Williams and the wizards that work their magic for them.