Allyltin compounds

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). 

Allyltin compounds can also be formed by elimination from the tin derivatives of allyldialkylcarbinols (145). 

Allyl silanes react with epoxides, in the presence of Bp3-OEt2 to give 2-allyl alcohols. The reaction of a-bromo lactones and CH2=CHCH2Si SiMe3)3 and AIBN leads to the a-allyl lactone. " Benzyl silanes coupled with allyl silanes to give ArCH2—R derivatives in the presence of VO(OEt)Cl2 " and allyltin compounds couple with allyl silanes in the presence of SnCU. " Allyl silanes couple to the a-carbon of amines under photolysis conditions. ... 

Hexamethylditin readily adds to allene in the presence of Pd(PPh3)4 to give an allyltin compound. An unsymmetrically substituted allene such as 1,1-dimethylal-lene undergoes kinetically controlled addition at lower temperatures, whereas at higher temperatures thermodynamically more stable products are formed (Scheme 16.61) [66],... 

Allyltin compounds, reaction with hexa-fluoroacetone, 30 232-233 Al NMR spectroscopy, 36 433-436 Alpha rays, kinetic data on, 3 202-203 Alumina... 

Allyltriphenyltin can also be prepared by using the reaction of preformed allylmagnesium bromide with triphenyltin chloride.2 However, the submitters prefer the simpler procedure described above for large-scale preparations of allyltin compounds. 

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... 

It is clear that allyltin compounds do add to allylpalladium complexes at the metal center and that these intermediates can be induced to undergo reductive elimination with maleic anhydride. In view of the phenyl- and vinyl-tin results (metal attack), it is tempting to assume all organotin reagents proceed by metal addition, but this remains to be verified. 

CALCULATION OF SECOND-ORDER RATE COEFFICIENTS (l.mole .sec" ) FOR THE IODINOLYSIS OF ALLYLTIN COMPOUNDS BY IODINE, REACTION (40), AT 25 °C... 

Allyltin compounds are unique players in radical chemistry, since they are able to serve both as radical acceptors and at the same time as radical chain mediators to provide tin radicals [27]. Because of the nucleophilic nature of ordinary alkyl radicals, the addition of an alkyl radical to tributylallyltin is not very fast, yet fast enough to transfer the radical chain [28], This is an advantage for the controlled... 

Free-radical-mediated four-component coupling reactions are rare. However, when an allyltin-mediated radical carbonylation is conducted in the presence of electron-deficient alkenes, four-component coupling reactions take place efficiently to give good yields of p-functionalized <5,fi-unsaturated ketones [40]. The wide scope of this four-component coupling reaction is noteworthy Primary, secondary, and tertiary alkyl bromides and iodides can be used as well as aromatic and vinylic halides. A variety of electron-deficient alkenes, such as methyl vinyl ketone, ethyl acrylate, acrolein, acrylonitrile, and vinyl sulfone, can be used as the acyl radical trap (Scheme 6.23). Fluorous allyltin compounds can also be used in four-component coupling reactions [41]. 

S.8.S.6.3. by Reaction of Allyltin Compound with Transition- or Inner Transition-Metal-Carbonyl and Other Complexes. 

Table 4. BF3-promoted additions of allyltin compounds to aldehydes.

Allyltin compounds readily add to aldehydes and ketones. Allylic bromides react with tin to generate the organometallic in situ, which then adds to aldehydes. Allylic chlorides react with aldehydes in the presence of ditin compounds such as MesSn—SnMes and a palladium catalyst. Allyltrialkyltin compounds ... 

With the exception of photochemical reactions, the chemistry of allyltin compounds is analogous to that of allylsilanes and translates to the use of acetylenic tin reagents. As a final illustration of the utility of tin reagents to the formation of C-glycosides, the use of acetylenic tin reagents, shown in Scheme 7.20, is addressed. In the cited report, Zhai et al. [98] observed the formation of a-C-acetylenic glycosides in good yields. The reactions were catalyzed by zinc chloride and run in carbon tetrachloride. 

Kosugi, M., Sasazawa, K., Shimizu, Y., Migita, T. Reactions of allyltin compounds. III. Allylation of aromatic halides with allyltributyltin in the presence of tetrakis(triphenylphosphine)palladium ° . Chem. Lett. 1977, 301-302. 

Unsaturated ketones can be readily synthesized by a three-component coupling reaction, comprised of alkyl halides, CO, and allyltin reagents [53]. Because of the slow direct addition of alkyl radicals to allyltin compounds [54], radical carbonylation with allyltin can be conducted at relatively low CO pressures to give good yields of y ,y-unsaturated ketones (Scheme 4-29). 

Allyltin compounds are most stable in the conformation in which the C-Sn bond lies parallel with the axis of the 7i-system, so that the c-7t overlap is maximised (see Section 9.1.2).27... 

Allyltin compounds can be prepared by the standard methods (Chapter 4) of the reaction of an allylmetallic compound with a tin halide, or of a stannylmetallic compound with an allyl halide, or of tin metal or a tin(II) compound with an allyl halide. There are, further, some special methods that depend on the presence of the double bond. 

Transmetallation reactions between allyltin compounds and other Lewis acid metal halides (e.g. Bu2SnCl2, BCI3, BBr AICI3, or TiCU) are similarly very fast,39 and the reaction between allyltriphenyltin and BCI3 (though not BF3-OEt2) is complete within one second.40 Reactions of this type have been used for preparing allylic derivatives of boron,41,42 indium,10,38 copper 43 phosphorus, arsenic, antimony,44 and other metals. 

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... 

The two principal routes to the organotin peroxides involve substitution by a peroxide nucleophile at a tin centre (equations 14-69 and 14-70), or (pericyclic) reaction of an allyltin compound with singlet oxygen (equation 14-71). Distannyl peroxides have also been prepared by the (homolytic) reaction of distannanes with triplet oxygen (equation 14-72). 

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