Diallyltin dibromide

Mediated by Tin. In 1983, Nokami et al. observed an acceleration of the reaction rate during the allylation of carbonyl compounds with diallyltin dibromide in ether through the addition of water to the reaction mixture.74 In one case, by the use of a 1 1 mixture of ether/water as solvent, benzaldehyde was allylated in 75% yield in 1.5 h, while the same reaction gave only less than 50% yield in a variety of other organic solvents such as ether, benzene, or ethyl acetate, even after a reaction time of 10 h. The reaction was equally successful with a combination of allyl bromide, tin metal, and a catalytic amount of hydrobromic acid. In the latter case, the addition of metallic aluminum powder or foil to the reaction mixture dramatically improved the yield of the product. The use of allyl chloride for such a reaction,... 

MeOH/AcOH-(Allyl)2SnBr2-(Pt) system at 50 55 °C. As illustrated in Scheme 149 [530], diallyltin dibromide (428) produced from metalKc Sn and allyl bromide in methanol reacts with carbonyl compounds (426) to give the allylated products (427) together with allyldibromotin monomethox-ide (430). The latter compound (430) may be reduced at the cathode to di- or zero-valent Sn, which reacts smoothly with allyl bromide to regenerate diallyltin di-bromide (428). 

The asymmetric allylation reaction of achiral aldehydes with diallyltin dibromide has been achieved by using the chiral diamine 1 as a promoter (eq 19). The enantiomeric excess increases up to 79% by using a chiral diamine similar to 1 which possesses an w-butyl group on the nitrogen of the pyrrolidine ring. ... 

In a similar vein, allylic iodides and, to a lesser extent, bromides undergo Barbier addition to aldehydes in the presence of activated tin powder in THF (Table 29) [45]. The reaction is thought to involve a diallyltin dihalide intermediate. Similar results were obtained when diallyltin dibromide, prepared independently, was used for the addition. 

The reaction involves stirring aldehyde, allyl bromide, and stannous chloride in water and applying an electrolytic potential of 2.0 V with graphite electrodes. The cathode rednces Sn(ll or IV) salts to tin metal, which react with allyl bromide to generate allyltin(ll) bromide and diallyltin dibromide. These organotin species then allylate the aldehyde and the resulting homoallyl alcohol is extracted with diethyl... 

The allylation of aldehydes via organotin reagents displays a negative activation volume [76]. As a matter of fact, the allylation of benzaldehyde with diallyltin dibromide is accelerated by addition of water [77]. The reaction was extended to various aldehydes and ketones and to various allylic organotin dichlorides [78] or tet-raallyltin in acidic aqueous medium [79]. With scandium triflate as a catalyst, tet-... 

Cyanohydrins. The organotin compound catalyzes the Mukaiyama aldol reaction, the derivatization of carbonyl compounds with MejSiCN, and other Lewis acid-catalyzed processes at -78°. It is prepared from diallyltin dibromide by reaction with pentafluorophenylmagnesium bromide followed by bromolysis. 

Di-f-butyl tartrate and tin(II) catecholate, together with Cul and DBU, promote the allylation of aromatic aldehydes, producing homoallylic alcohols with high ee values. Diallyltin dibromide in the presence of the N-butyl-2-piperidinomethylpyrrolidine 38 also gives useful results. ... 

Mediated by Tin. In 1983, Nokami et al. observed an acceleration of the reaction rate during the allylation of carbonyl compounds with diallyltin dibromide in ether through the addition of water to the reaction mixture. " In one case, by the use of a 1 1 mixture of ether/water as solvent, benzaldehyde was allylated in 75% yield in... 

Recently, nanometer tin-mediated allylation of aldehydes or ketones in distilled or tap water gave rise to homoallyl alcohols in high yield without any other assistance such as heat or supersonic or acidic media (Eq. 8.41). Allylation of P-keto aldehydes and functionalized imines by diallyltin dibromide was carried out to generate skipped and conjugated dienes. Aldehydes are allylated with CH2=CHCH2SnBu3 using Sn catalysts in acidic aqueous media. Exclusive aldehyde selectivity was observed for competitive reactions of aldehydes and ketones in the presence of 5 mol% of (CH2=CHCH2)4Sn or SnCU in a mixture of aqueous HCl and THE (Eq. 8.42). ... 

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... 

In basic aqueous media, a kinetic study of the reaction between stannate(II) ions and alkyl halide shows that mono- and disubstituted organotin compounds are formed (Eq. 6.12a).27 The monosubstituted organotin compound is obtained after a nucleophilic substitution catalyzed by a complexation between the tin(II) and the halide atom. The disubstituted compound results from an electrophilic substitution coupled with a redox reaction on a complex between the monosubstituted organotin compound and the stannate(II) ion. Stannate(IV) ions prevent the synthesis of the disubstituted compound by complexation. Similarly, when allyl bromide and tin were stirred in D2O at 60° C, allyltin(II) bromide was formed first. This was followed by further reaction with another molecule of allyl bromide to give diallyltin(IV) dibromide (Eq. 6.12b).28... 

The nature of the organotin intermediates has been studied. It was found that when allyl bromide and tin reacted in aqueous media, allyltin(II) bromide was first formed and then was followed by the formation of diallyltin(IV) dibromide (See also Section 6.4.1, Eq. 6.12b). Either of the two organotin intermediates can react with carbonyl compounds to give the corresponding homoallylic alcohols. However, the tin(II) species was found to be more reactive than the tin(IV) species (Eq. 8.38).81... 

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