[208164-59-4]  · C16H33ISn  · (MW 471.03)

(bifunctional reagent for cyclohexenone annulations2)

Alternate Names: [(Z)-4-iodobut-1-enyl]tributylstannane.

Physical Data: colorless liquid.

Solubility: soluble in THF, diethyl ether, CHCl3.

Preparative Methods: sequential treatment of acetylene with Bu3SnCu(Bu)(CN)Li2 and ethylene oxide provides (Z)-4-tributylstannylbut-3-en-1-ol (1)3 which, upon treatment with Ph3P·I2, affords the title reagent (2) (1).2

Handling, Storage, and Precautions: organostannane compounds are toxic and must be prepared, purified, and used in a fume hood.4

Cyclohexenone Annulation

Treatment of dimethylhydrazone (3) with LDA, followed by addition of a mixture of the title reagent (2) and HMPA, gives the alkylated hydrazone (4). Stereospecific iododestannylation5 and hydrolysis of the hydrazone provides vinyl iodide (5), which readily undergoes ring closure upon treatment with n-butyllithium. Oxidation of the resultant tertiary allylic alcohol (6) with PCC on alumina affords the corresponding cyclohexenone (7).

Annulation of substrates containing ketal groups (3) and seven-membered rings (4) exemplifies the efficacy of the process.

Related Reagents.

Cycloheptenones are obtained by application of the above protocol using (Z)-5-iodo-1-(tributylstannyl)pent-1-ene (8) (5).6 Rate acceleration and cleaner products are noted when the PCC oxidations of the intermediate tertiary allylic alcohols are performed in the presence of 3Å molecular sieves. Cyclic b-keto ester substrates have also been annulated (6).6

The cyclization step is highly chemoselective and products that would have been produced from ring closure on the ester carbonyl functions were not detected.

1. Hartley, R. C.; Caldwell, S. T., J. Chem. Soc., Perkin Trans 1 2000, 477.
2. Piers, E.; Boulet, S. L., Synlett 1998, 517.
3. Barbero, A.; Cuadrado, P.; Fleming, I.; González, A. M.; Pulido, F. J.; Rubio, R., J. Chem. Soc., Perkin Trans 1 1993, 1657.
4. Neumann, W. P., The Organic Chemistry of Tin; Interscience: New York, 1970, 230-237.
5. Piers, E.; Coish, P. D., Synthesis 1995, 47.
6. Piers, E.; Walker, S. D.; Armbrust, R., J. Chem. Soc., Perkin Trans 1 2000, 635.

Edward Piers & Denise L. Andersen

University of British Columbia Vancouver, British Columbia, Canada

Copyright 1995-2000 by John Wiley & Sons, Ltd. All rights reserved.