Formylsilanes. Chemoenzymatic and Chemical Syntheses of the 2,4-Dinitrophenylhydrazones of These Apparently Air- and Water-Stable Compounds

Formylsilanes have long been reported to be notoriously unstable compounds. In fact, no formylsilane has been reported that was stable in air or in water nor are there any known hydrates, imines, or hydrazones of formylsilanes. We have found that monoamine oxidase catalyzes the oxidation of (aminomethyl)-tert-butyldimethylsilane in aqueous buffer at pH 9 to give, apparently, either formyl-tert-butyldimethylsilane or the corresponding hydrate, which is isolated as the 2,4-dinitrophenylhydrazone. The chemical synthesis of this same compound and the corresponding formyltrimethylsilane was carried out in low yields by a standard route to acylailanes but in good yields by a new route involving conversion of (1,3-dioxolan-2-yl)tri-n-butylstannane to the corresponding silanes followed by acid hydrolysis. Although the formylsilane could not be isolated, it or its hydrate apparently is stable enough in water to survive incubation for several hours prior to the 2,4-dinitrophenylhydrazine trapping reaction.