Allylation of carbonyl compounds mediated by tin

The aqueous allylation reaction mediated by tin was inspired by the observation that allylation of benzaldehyde with diallyltin dibromide seemed to be accelerated by the addition of water (Nokami et al, 1983). Acidic conditions (HBr, AcOH) were needed to perform the heterogeneous reaction using 

With functionalized allylic bromides, the same procedure allowed preparation of bromo-homoallylic alcohols and 1,3-ketoacetates (Mandai et al., 1984) or a-methylene-y-butyrolactones (Nokami et al., 1986). 

An improvement of the allylation reaction was achieved with the use of ultrasonic waves in a water-tetrahydrofuran (5/1) mixture without the help of acidic co-reagents (Petrier et al., 1985). Noteworthy are the sonicated reactions involving commercially available aqueous solutions of aldehydes, such as formaldehyde, and those involving aldehydes containing free hydroxyl groups (Einhom and Luche, 1987)  

When applied to carbohydrates, the sono-allylation proceeded with useful diastereoselectivity (rAreo-selectivity) and allowed preparation of higher-carbon sugars from water-soluble substrates directly in aqueous ethanol without protection (Schmid and Whitesides, 1991). Later, the authors showed that the allylation of aldoses could be advantageously carried out by heating the reaction mixture for example, the allylation of D-arabinose required 16-20h under sonication, but only 2h under reflux (Kim et al., 1993)  

Of interest was the use of a suspension of tin powder in a saturated aqueous NH4CI/THF solution at 60°C (Zhou et al., 1992). 

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