[82097-93-6]  · C12H27CuSn  · Tri-n-butylstannylcopper  · (MW 353.65)

(incorporation of tributyltin via reaction with electrophilic substrates1-6)

Physical Data: prepared in situ; its THF solution is dark red.

Solubility: sol THF.

Preparative Methods: Bu3SnCu (1) is prepared by reaction of Tri-n-butylstannyllithium with 1 equiv of Copper(I) Iodide (eq 1).1,2,5,8 A closely related reagent, Bu3SnCu.Me2S (see Trimethylstannylcopper-Dimethyl Sulfide), is readily obtained by treatment of Bu3SnLi with an equimolar quantity of CuBr.Me2S (2) (see Copper(I) Bromide) (eq 2).3,4,9-13

Handling, Storage, and Precautions: should be prepared in dry solvent and used under an inert atmosphere. Organotin compounds are toxic;7 therefore, reaction workup should be carried out in a fume hood.

Substitution Reactions.

Bu3SnCu (1) reacts with methyl 3-chloro- and 3-iodoacrylates to produce the corresponding 3-tributylstannylacrylates. These reactions, which presumably proceed via a conjugate addition-elimination mechanism, occur under mild conditions and, importantly, are stereospecific (eqs 3 and 4).1 In similar fashion, treatment of ethyl (Z)-3-(p-tolylsulfonyloxy)acrylate with (1) provides, stereoselectively, ethyl (Z)-3-tributylstannylacrylate (eq 5).1

In a related process, reagent (1) reacts with (E)-2-chloro-1-(phenylsulfonyl)ethylene to provide the corresponding tributylstannane (eq 6),2 a useful intermediate for the synthesis of 1-tributylstannyl-1-alken-3-ols.2

Tributylstannylcopper replaces the 4-iodo group of the functionalized pyrimidines (3) and (4) (eq 7).5 The stannylated products (5) and (6) are valuable for the preparation of substituted pyrimidine derivatives.5

Reactions with Alkynic Substrates.

Reagent (2) is very useful for effecting the highly stereocontrolled conversion of a,b-alkynic esters into alkyl (E)-3-tributylstannyl-2-alkenoates.3,9,11 -13 Examples are given in eqs 8 and 9.11,12 The (E)-3-tributylstannyl-2-alkenoates are valuable synthetic intermediates that have been employed as precursors to radical cyclization substrates,9,11,12 to configurationally defined alkenyllithium reagents,3,13 and in natural product synthesis.3,9,13 For instance, compounds (7) (eq 8) and (8) (eq 9) have been transformed into the intermediates (9) and (10), respectively. Radical-mediated cyclization of (9) provides primarily the highly functionalized heterocycle (11) (eq 10),11 while treatment of (10) with bis(cyclopentadienyl)titanium(III) chloride gives the ester alcohol (12) with high stereoselectivity (eq 11).12 Additionally, (13), derived by reaction of ethyl 2-pentynoate with (2),3 is readily converted into (14). The latter substance is a convenient precursor to (Z)-3-lithio-2-pentene (15), which played an important role in a total synthesis of the unusual natural product triophamine (16).3

Reagent (2) can also be employed to achieve the stereoselective cis-addition of the elements of Bu3Sn-H across the triple bond of propargylic alcohols. Examples are given in eqs 12 and 13.4,6,10 Substance (17) has been used in the synthesis of novel compounds structurally related to the enediyne antibiotic dynemycin A.6 The diol stannane (18) has served as an excellent precursor for the preparation of 3-lithiofuran4 and 2-tributylstannyl-1,3-butadiene.14 Diels-Alder reactions of the latter material have been investigated.10,14

Related Reagents.

Bis(methylthio)(trimethylstannyl)methane; 2,3-Bis(trimethylstannyl)-1,3-butadiene; 4-Chloro-2-trimethylstannyl-1-butene; (E)-1-Lithio-2-tributylstannylethylene; Lithium Phenylthio(trimethylstannyl)cuprate; Methyl Tributylstannyl Sulfide; trans-1,2-Bis(tributylstannyl)ethylene; Tri-n-butylstannylacetylene; Tri-n-butylstannyllithium; Trimethylstannylcopper-Dimethyl Sulfide; 2-Trimethylstannylmethyl-1,3-butadiene; Trimethylstannyllithium; (Triphenylstannylmethyl)lithium.

1. Seitz, D. E.; Lee, S.-H. TL 1981, 22, 4909.
2. Ochiai, M.; Ukita, T.; Fujita, E. TL 1983, 24, 4025.
3. Piers, E.; Chong, J. M.; Gustafson, K.; Andersen, R. J. CJC 1984, 62, 1.
4. Fleming, I.; Taddei, M. S 1985, 898.
5. Majeed, A. J.; Antonsen, O.; Benneche, T.; Undheim, K. T 1989, 45, 993.
6. Porco, J. A., Jr.; Schoenen, F. J.; Stout, T. J.; Clardy, J.; Schreiber, S. L. JACS 1990, 112, 7410.
7. Pereyre, M.; Quintard, J.-P.; Rahm, A. Tin in Organic Synthesis; Butterworth: London, 1987; pp 6-7.
8. Gallardo V., M. T.; Zapata, A. SC 1987, 17, 1165.
9. Harris, F. L.; Weiler, L. TL 1987, 28, 2941.
10. Nativi, C.; Taddei, M.; Mann, A. T 1989, 45, 1131.
11. Munt, S. P.; Thomas, E. J. CC 1989, 480.
12. Lowinger, T. B.; Weiler, L. CJC 1990, 68, 1636.
13. Dodd, D. S.; Pierce, H. D., Jr.; Oehlschlager, A. C. JOC 1992, 57, 5250.
14. Fleming, I.; Taddei, M. S 1985, 899.

Edward Piers & Christine Rogers

University of British Columbia, Vancouver, BC, Canada

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