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By: , Aldrich ChemFiles 2006, 6.6, 6.

Aldrich ChemFiles 2006, 6.6, 6.

Alkynes have been used for many years in the Sonogashira coupling reaction1 and related Castro-Stephens reaction,2 and have recently gained considerable interest in the Huisgen 1,3- dipolar cycloaddition with organic azides.3

Recently, Walsh demonstrated the use of terminal alkynes in the asymmetric vinylation and dienylation of ketones (Scheme 6).4 In separate communications, Trost5 and Shibasaki6 have described the use of terminal alkynes in the asymmetric alkynylation of aldehydes to obtain propargylic alcohols (Scheme 7). Additionally, Trost has used terminal and internal alkynes in a regioselective hydrosilylation to obtain a-vinylsilanes and trisubstituted (Z)-vinylsilanes, respectively (Scheme 8).7

Scheme 6

Scheme 7

Scheme 8

Not only can propargylic alcohols be hydrosilylated as in Scheme 8, they can also undergo aldol-type reactions to obtain enones,8 or be elaborated to obtain highly substituted chiral allenes via a stereoselective Saucy–Marbet rearrangement.9 They have been recently employed in the synthesis of pyrimidines or pyridines in a one-pot tandem oxidation-heteroannulation with amidines or enamines (Scheme 9).10 Brummond has used propargylic alcohols to synthesize allenic amino acids, which are further elaborated to obtain a series of structurally unique heterocycles (Scheme 10).11

Scheme 9

Scheme 10

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  1. Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett. 1975, 4467.
  2. Stephens, R. D.; Castro, C. E. J. Org. Chem. 1963, 28, 3313.
  3. Huisgen, R. In 1,3-Dipolar Cycloaddition Chemistry; Padwa, A.; Ed.; Wiley: New York, 1984; Vol. 1, p 1.
  4. (a) Li, H.; Walsh, P. J. J. Am. Chem. Soc. 2005, 127, 8355. (b) Li, H.; Walsh, P. J. J. Am. Chem. Soc. 2004, 126, 6538.
  5. Trost, B. M. et al. J. Am. Chem. Soc. 2006, 128, 8.
  6. Takita, R. et al. J. Am. Chem. Soc. 2005, 127, 13760.
  7. Trost, B. M.; Ball Z. T. J. Am. Chem. Soc. 2005, 127, 17644.
  8. Trost, B. M.; Oi, S. J. Am. Chem. Soc. 2001, 123, 1230.
  9. Kurtz, K. C. M. et al. Tetrahedron 2006, 62, 3928.
  10. Bagley, M. C. et al. Synlett 2003, 1443.
  11. Brummond, K. M.; Mitasev, B. Org. Lett. 2004, 6, 2245.

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