Stannyldienes, New Tools For Organic-synthesis - Preparation and Reactivity

Tributylstannyl-1,3-dienes could be considered synthetic equivalents of conjugated dienic anions. The preparation of differently substituted 2- and 3-trialkylstannyl-1,3-dienes is reported starting from propargyltrimethylsllane. The position of the stannyl moiety on the dienic skeleton can be controlled by hydrostannylation of (trimethylsilyl)propargyl alcohols or stannyl cupration of (trimethylsilyl)propargyl ketones. The so obtained stannyldienes are submitted to Dienes Alder reaction and the corresponding cycloadducts functionalized through theC-Sn bond. Stannyldienes are also suitable for a regiocontrolled transfer of the dienic structure by : a)tin-lithium exchange and further reaction with aldehydes to give conjugated dienic alcohols; b)coupling with acyl chlorides in the presence of palladium catalysts to give conjugated dienic ketones; c) AlCl3, promoted reaction with acyl chlorides to give allenic ketones.