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Copper catalysed coupling of alkynes and iodoalkynes; diynes

SyntheticPage 25
DOI: 10.1039/SP25
Submitted Jul 03, 2001, published Jul 03, 2001
zac etheridge (zac.etheridge@orange.net)
A contribution from Caddick, Sussex


			Reaction Scheme: <IMG src="/images/empty.gif">Copper catalysed coupling of alkynes and iodoalkynes<IMG src="/images/empty.gif">

Chemicals Used

(2S)-4-Iodo-3-butyne-1,2-diol (320mg, 1 equiv.)
1-tert-Butyldimethylsilyloxyprop-2-yne (462mg, 1.8 equiv.)
Copper(I) iodide (washed with dry THF and dried in vacuum, 29mg, 0.1 equiv.)
Pyrrolidine (freshly distilled, 1.5 mL, 1 mL/mmol

Procedure

The two alkynes are stirred together at 0 oC in pyrrolidine and the copper iodide is added in one portion, initially creating a green coloured solution which quickly turns red/brown. The reaction is stirred at this temperature for 30 minutes-1 hour until completion (TLC), then quenched with ammonium chloride solution, extracted 4 times with ether, washed with brine, dreid over magnesium sulphate, filtered and concentrated. Purification is achieved by column chromatography eluting with 20-50% EtOAc/PE.

Author's Comments

In order to attain reliable yields, purification of reagents as detailed is necessary and the reaction must be kept at 0oC (although not all substrates require reduced temperatures; see lead reference). It should be monitored regularly by TLC as it can proceed very rapidly, and decomposition will occur if the reaction is continued stirring after it is complete. If these conditions are observed, yields of greater than 80% are possible. Further examples carried out include the coupling of triethylsilylacetylene, although due to the reduced stability if the TES group, the yields tend to be somewhat less (60-70%). It is also interesting to note that the reaction fails completely with trimethylsilylacetylene, presumably due to the lability of the TMS group.

Data

1H NMR (300MHz, CDCl3) d 4.40 (1H, t, J=4.6), 4.26 (2H, s), 3.56-3.66 (2H, m), 2.26 (1H, br s, exch.), 1.95 (1H, br s, exch.), 0.78 (9H, s), 0.00 (6H, s).

Lead Reference

Alami M., Ferri F. Tetrahedron Lett. 1996 p.2763

Other References

Hirama M., Iguchi S., Wang G.X. J. Org. Chem. 2001 p.2146

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Keywords: alkyne, copper catalyst, copper coupling, diyne, iodoalkyne, organometallics (please give metal & ligand types in box)

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