Tributyltin ethoxide

Evidence that the enol form is more reactive than the keto form is shown in Scheme 14-4. Tributyltin ethoxide reacts with ketene at -78 °C to give the ketene acetal, which at the same temperature adds to benzaldehyde to give the hydroxyester. However, if the enolate is allowed to stand at 0 °C for several hours before the aldehyde is added at that temperature, no reaction occurs.116... 

Figure 6.2.6 Formation of methyl-N-phenylcarbamate and tributyltin ethoxide...

Hexabutyldistannane, which is an important reagent in many organic syntheses, can be prepared very conveniently by reducing bis(tributyltin) oxide with sodium borohydride in ethanol at room temperature. After 5 min, the only tin species present is tributyltin hydride, but in 2 h, its decomposition is catalyzed by the ethoxide ion that is formed to give the distannane in 83% yield.444 Hexaalkyldistannanes, R3SnSnR3 (R = Et, Pr, or Bu), are obtained in ca. 50% yield when the corresponding trialkyltin halides are treated with zinc powder in THF.445... 

The reduction of bis(tributyltin) oxide with sodium borohydride in ethanol apparently falls into this group of reactions. After 5 min, the only tin compound present is tribu-tyltin hydride, but, during 2 h, this is converted into hexabutylditin in good yield. The catalyst for the decomposition of the hydride appears to be the ethoxide ion which is generated from the NaBH4 and ethanol.22... 

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