Allyltin compounds reaction with aldehydes

Alfylations. A direct preparation of allyltin reagents from allyl halides is accomplished by treatment with SnCl. Allytributylstannane is activated by SnClj in MeCN for reaction with carbonyl compounds and imines. Allylic alcohols and cyclic carbonates can also be used as allylating agents for amines and aldehydes, respectively. 

Allyltin compounds can be prepared by simple modifications of the usual reaction involving allyl Grignard reagents (139), by the 1,4-addition of trialkyltin hydrides to 1,3-dienes 140,141), or by the reaction of an aldehyde or ketone with the appropriate, tin-carrying, Wittig reagents (142). 

An interesting approach to carbobicyclic polyhydroxylated compounds was proposed by Jarosz.43 It was based on a Lewis acid transformation of sugar allyltins 82 into dieno-aldehydes 83 with the fi-geometry across the internal double bond exclusively. The Wittig-type reaction of 83 afforded a triene, which underwent cyclization under high pressure, providing derivatives of bicyclo[4.3.0]nonane 84. Alternatively, dienoaldehyde 83 was converted into the phosphonate 85, which afforded the bicyclo[4.4.0]-decene derivatives (86) upon reaction with an aldehyde and simultaneous cyclization of the resulting triene.43 (Fig. 29). 

BuySnAl(CjHs)2 (12, 339-341). Reaction of allylic phosphates with this reagent (1) and a Pd(0) catalyst affords allyltin compounds, which react with aldehydes to produce homoallylic alcohols in 65-85% yield. The reaction involves predominant inversion of stereochemistry.1... 

Sugar allyltin derivatives are very useful synthetic intermediates. The most convenient and reliable method for their preparation is a so-called xanthate procedure. The first compound of this class was prepared in 1988 by Mortlock and Thomas [74]. 1,2-0-isopropylidene-D-glycer-aldehyde (80) was converted into allylic alcohol and further transformed into the corresponding xanthate 81. This compound underwent thermal [3,3] rearrangement into the dithiocarbon-ate 81a, which upon reaction with tri-n-butyltin hydride provided the final sugar allyltin 82 as a mixture of isomers with the E-one strongly predominating (O Scheme 35). 

Allyltin compounds are useful in organic synthesis as a non-basic source of a weakly nucleophilic allyl group. Electrophiles usually react in a y-anti (Se2 ) sense, which involves allylic rearrangement. (Some multiply-bonded electrophiles such as SO2 and aldehydes are exceptional in that they react with. s vn-stercochemistry, but these reactions are perhaps better regarded as ene-reactions, and are considered as such in Section 9.1.3.4). Thus the acidolysis of a mixture of methylcyclohepten-2-ylstannanes proceeds as shown in equation 9-16. 46 Reactions of this type can be used for the allyhc isomerisation of terpene hydrocarbons, for example of (+)-a-pinene into (+)-P-pinene (equation 9-17).47... 

In attempts to prepare homoallyl alcohol in an environmental friendly process, Andrews and co-workers reported its synthesis using a solvent-free method mediated by tin under ultrasound. Experiments showed that the alcohols were produced in excellent yields with aldehydes but that no products were produced using ketones. However, the existence of toxic allyltin compounds in the final products prevented the method from being applied downstream in fine chemical applications. On the other hand, according to Wang et carbonyl allylation reactions mediated by SnCl2 in aqueous solution without a Lewis acid under ultrasonic irradiation were successfully carried out. 

In Section 12.7.B, the Stille coupling reaction reacted a vinyl tin compound with a vinyl triflate, in the presence of palladium(O). Tetravalent tin complexes add to aldehydes and ketones, in the presence of a Lewis acid. Allyltin complexes are, by far, the most widely used of these compounds.297 a typical example is taken from the work of Keck, in which a chiral aldehyde (455) was treated with allyltributyltin, in the presence of various Lewis acids. S As shown in Table 12.19, a mixture of syn (456) and anti (457) products was obtained. The ratio of 456/457 was dependent on the structure of the R group in 455, the solvent and the Lewis acid.The anti product (457) was obtained by using the tert-butyldimethylsilyloxy derivative (sec. 7.3.A.i) of 455 with 2 equivalents of boron trifluoride in dichloromethane. The syn product is obtained preferentially when the benzyloxy derivative of 455 is used with titanium tetrachloride in dichloromethane.298... 

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