[73927-91-0]  · C14H29IO2Sn  · Tri-n-butyl(iodoacetoxy)stannane  · (MW 475.04)

(g-lactone preparation;2 annulation)

Alternate Names: tributylstannyl iodoacetate; tributyl(iodoacetoxy)tin.

Physical Data: mp 94.4 °C.

Solubility: insol cold H2O; sol THF, CH2Cl2, acetone, alcohol.

Preparative Method: 3 two equiv of iodoacetic acid and one equiv of Bis(tri-n-butyltin) Oxide are heated to 130 °C for 30 min. The cooled mixture is extracted with hot hexanes. The hexanes are removed in vacuo to afford tributyl(iodoacetoxy)tin. This preparation generates a product sufficiently pure for use in the reactions described below.

Handling, Storage, and Precautions: best results are obtained if the reagent is used within one week of the date of preparation. Use in a fume hood.

General Discussion.

Tributyl(iodoacetoxy)tin is readily prepared by the reaction of bis(tri-n-butyltin) oxide and iodoacetic acid.3 This reaction has general applicability for the preparation of other halo esters and of higher homologs. By using this reagent in the presence of Azobisisobutyronitrile, many alkenes can be converted into g-lactones in a single step (eq 1). The reaction of tributyl(iodoacetoxy)tin with alkenes proceeds by way of a radical mechanism.4 As illustrated in eq 2, the mechanism involves a radical chain reaction beginning with homolytic cleavage of the carbon-iodine bond followed by radical addition to the alkene. The reaction of the resulting radical with a molecule of tributyl(iodoacetoxy)tin followed by a rapid cyclization with concurrent loss of tributyliodotin completes the mechanism. Because of the electrophilic nature of the radical, this reaction proceeds well with electron-rich alkenes. Electron-deficient alkenes do not react.

This reaction has been used for the preparation of a bicyclic furo[2,3-b]furan subunit (eq 3) in the synthesis of clerodane terpenes.5 The intramolecular variant of this reaction has also been reported.1 In this case a strained bicyclic lactone is formed in 40% yield (eq 4).

1. Kraus, G. A.; Landgrebe, K. T 1985, 41, 4039.
2. Degueil-Castaing, M.; De Jeso, B.; Kraus, G. A.; Landgrebe, K.; Maillard, B. TL 1986, 27, 5927.
3. Anderson, H. H. JOC 1957, 22, 147.
4. Kraus, G. A.; Landgrebe, K. TL 1984, 25, 3939.
5. Pezechk, M.; Brunetiere, A. P.; Lallemand, J. Y. TL 1986, 27, 3715.

George A. Kraus

Iowa State University of Science and Technology, Ames, IA, USA

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