Allyldibutyltin Chloride1

[64549-05-9]  · C11H23ClSn  · Allyldibutyltin Chloride  · (MW 309.46)

(versatile reagent, together with other related halides, for the allylation of carbonyl compounds to form homoallylic alcohols,2 halotetrahydropyrans,3 allyl ethers,4 alkenyl-N-alkyl carbamates,5 and esters6)

Alternate Names: allyldibutylchlorotin; dibutylchloro-2-propenylstannane.

Physical Data: bp 103 °C/15 mmHg; d 1.2 g cm-3.

Solubility: insol cold water, sol alcohols and common organic solvents.

Form Supplied in: colorless liquid; commerically unavailable. Drying: the usual procedure is vacuum distillation. A saturated aqueous solution of allyldibutyl tin chloride disproportionates to diallyldibutyltin and dibutyltin dichloride; protonolysis of the allyl-tin bond is very slow.

Handling, Storage, and Precautions: very easy to handle without special precautions. Nevertheless, storage in the refrigerator and in dark bottles is recommended. Its toxicity has been determined to be comparable to that of Tri-n-butylchlorostannane. Use in a fume hood.

Preparation of Allyltin Halides.

A list of isolated and well-established allyltin halides is provided in Table 1, together with procedures for their preparation.

The general procedures for preparing allyltin halides listed in Table 1 are as follows.

Redistribution (R) reactions of allyl- and mixed allylorgano-tins with organotin or tin(IV) halides (eqs 1 and 2).1c,2a-d,3a,8

Reversible allylstannation (RA), i.e. thermal decomposition of b-organostannoxyalkenes of the type Bu3 - nClnSn--O--CRR-CHR-CH=CH2 where n = 1 and 2, R, R are alkyl groups, and R is H or Me (eq 3).2c,7,10-12

Direct synthesis (DS), i.e. oxidative additions of tin(II) halides to allyl halides (eq 4).1c,2c,12

Cleavage (C) of appropriate unsymmetrical organotins (eq 5).9

The redistribution reaction is one of the most efficient preparation methods because many allyltin halides can be generated and used in situ,1c e.g. the system Bu3SnCH2CH=CH2/SnCl4 gives rise to CH2=CH-CH2SnCl3. In the same way, the unstable isomers R3 - nXnSnCH(CH3)CH=CH2 (n = 1-3) can be prepared in situ and then allowed to react with selected substrates.13

Allylstannation of Carbonyl Compounds with Allyltin Halides.

When allyldibutyltin chloride is allowed to react with aldehydes and ketones, exothermic additions take place, affording homoallylic alcohols in good yields (eq 6).2a,c The reactions occur under mild conditions. They can be carried out neat, in solution, or in the presence of air or water.14

The tin atom in allyltin halides possesses enhanced electrophilic character compared to the parent compounds R3SnAll (All = allyl or allylic group), which are chemically inert towards carbonyl compounds under the same conditions. The Lewis acidity of tin seems to be the driving force for the high reactivity since allylation can be efficiently achieved at -78 °C (eq 7).15

The following order of reactivity has been found: BrCl2SnAll > BuCl2SnAll > Bu2ClSnAll >> Bu3SnAll. Allylstannation of carbonyl compounds by these reagents can be performed in the presence of water to afford homoallylic alcohols directly. It can be carried out even in the presence of an acidic aqueous solution of HClO4 (0.1-4 M).14d When crotyltins are used, the stereochemical outcome depends on the acid concentration. As a matter of fact, the stereochemical course of crotylstannation reactions, that is the recovery of anti and/or syn as well as (E) and/or (Z) homoallylic alcohols, starting from isomeric mixtures of (E/Z)-crotyltin derivatives, depends on the experimental conditions. Poor anti selectivity (<=66%) results from reactions of some aldehydes with isomeric mixtures of isolated crotyltins,2d while syn selectivity (72-77%) is encountered when equilibrated mixtures of the system (E/Z)-Bu3SnCrot/Bu2SnCl2 are employed.2f (Z) Selectivity (89-100%) occurs when the unstable isomer Bu2ClSnCH(Me)CH=CH2 is generated in situ in the presence of the aldehydes (eq 8).13a,b

4-Halo-2,6-dialkyltetrahydropyrans are easily synthesized using allyltin di- and trihalide derivatives (eq 9).3a-e

(E/Z)-4-Halo-2,6-dialkyl-3-methyltetrahydropyrans are produced from the corresponding crotyl halides.3d Alkoxides of the type BuCl2Sn-O-CH(CH=CHR)CH2CH=CH2 and BuCl2-Sn--O--CH(CH=CHR)CH(R)CH=CH2 (R = Me or Pr, and R = Me), prepared via allylstannation of a,b-unsaturated aldehydes, give rise to isomeric mixtures of allyl ethers through an intermolecular reaction (eq 10).4

Alkenyl-N-alkyl carbamates can be produced in an one-pot synthesis by combining Bu2ClSnCH2CH=CH2, RCHO, and EtNCO (eq 11).5

Adduct A is formed through two distinct steps: step (a) deals with the selective allylstannation of the aldehyde to form adduct A (the insertion of EtNCO into the Sn-allyl bond does not occur), while the subsequent step (b) arises due to the ability of tin alkoxides to react with isocyanates.16

1. (a) Harrison, P. G. The Chemistry of Tin; Chapman & Hall: New York, 1989. (b) Pereyre, M.; Quintard, J.-P.; Rahm, A. Tin In Organic Synthesis; Butterworths: London, 1987. (c) Tagliavini, G. Rev. Si, Ge, Sn, Pb 1985, 8, 237.
2. (a) Tagliavini, G.; Peruzzo, V.; Plazzogna, G.; Marton, D. ICA 1977, 24, L47. (b) Peruzzo, V.; Tagliavini, G. JOM 1978, 162, 37. (c) Gambaro, A.; Peruzzo, V.; Plazzogna, G.; Tagliavini, G. JOM 1980, 197, 45. (d) Gambaro, A.; Marton, D.; Peruzzo, V.; Tagliavini, G. JOM 1982, 226, 149. (e) Boaretto, A.; Marton, D.; Silvestri, R.; Tagliavini, G. G 1985, 115, 391. (f) Boaretto, A.; Marton, D.; Tagliavini, G. JOM 1987, 321, 199.
3. (a) Gambaro, A.; Boaretto, A.; Marton, D.; Tagliavini, G. JOM 1983, 254, 293. (b) Boaretto, A.; Marton, D.; Tagliavini, G. ICA 1983, 77, L153. (c) Gambaro, A.; Boaretto, A.; Marton, D.; Tagliavini, G. JOM 1984, 260, 255. (d) Boaretto, A.; Furlani, D.; Marton, D.; Tagliavini, G.; Gambaro, A. JOM 1986, 299, 157. (e) Marton, D.; Furlani, D.; Tagliavini, G. G 1987, 117, 189.
4. Marton, D.; Furlani, D.; Tagliavini, G. G 1988, 118, 135.
5. Furlani, D.; Marton, D.; Tagliavini, G. G 1987, 117, 283.
6. Boaretto, A.; Marton, D.; Tagliavini, G. JOM 1985, 288, 283.
7. Peruzzo, V.; Tagliavini, G.; Gambaro, A. ICA 1979, 34, L263.
8. Cauletti, C.; Furlani, C.; Grandinetti, F.; Marton, D. JOM 1986, 315, 287.
9. Rosenberg, S. D.; Debreczeni, E.; Weinberg, E. L. JACS 1959, 81, 972.
10. Gambaro, A.; Marton, D.; Peruzzo, V.; Tagliavini, G. JOM 1981, 204, 191.
11. Gambaro, A.; Marton, D.; Tagliavini, G. JOM 1981, 210, 57.
12. Sisido, K.; Takeda, Y. JOC 1961, 26, 2301.
13. (a) Gambaro, A.; Ganis, P.; Marton, D.; Peruzzo, V.; Tagliavini, G. JOM 1982, 231, 307. (b) Boaretto, A.; Marton, D.; Tagliavini, G. ICA 1983, 77, L196.
14. (a) Boaretto, A.; Marton, D.; Tagliavini, G.; Gambaro, A. JOM 1985, 286, 9. (b) Boaretto, A.; Marton, D.; Tagliavini, G. JOM 1985, 297, 149. (c) Furlani, D.; Marton, D.; Tagliavini, G.; Zordan, M. JOM 1988, 341, 345. (d) Marton, D.; Tagliavini, G.; Vanzan, N. JOM 1989, 376, 269.
15. Mukaiyama, T.; Harada, T. CL 1981, 1527.
16. Davies, A. G.; Harrison, P. J. JCS(C) 1967, 298.

Giuseppe Tagliavini

University of Padua, Italy

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