Addition of O-H Bonds across Alkynes

Hydration of unactivated alkynes is an important method for functionalizing this plentiful hydrocarbon source. Therefore, a variety of metal ions have been proposed as catalysts for this reaction, and almost all of the reported additions of water to terminal alkynes follow the Markonikov rule. The hydration of 1-alkynes with Hg(II) salts in sulfuric acid [85], RuCb/aq.HCl [86, 87], K[Ru (edta-H)Cl]-2H20 [88], RhCl,.3H20/aq. HCl [89], RhCl3/NR4 [90], Zeise-type Pt(II) complexes [91-93], and NaAuCb [94] produced exclusively methyl ketones (Eq. 6.46). 

Several Pt(II) complexes are also effective for the hydration of internal alkynes (Eq. 6.48). Internal alkynes were converted to the corresponding internal ketones in 

The RuClj/aq. HCl system is effective for hydration of phenylpropiolic acid to give acetophenone and carbon dioxide via the P-keto acid (Eq. 6.53) [86]. 

The stereoselective catalyzed addition of water or methanol to dimethyl acetylenedicarboxylate (DMAD) was reported to yield oxalacetic acid dimethylester or dimethyl methoxyfumarate. The catalyst precursor cis-[Pd(PMe2Ph)2(solvent)2] [Bp4]2 was prepared from ds-[PdCl2(PMe2Ph)2] and AgBp4 (Eq. 6.54). The analogous platinum complex was not effective, however [99]. 

Recently Teles found that cationic gold(I) complexes of the general type [L-Au ] (where L is a phosphine, a phosphite or an arsine) were excellent catalysts for the ad- 

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