Asymmetric Hydroacylation Reactions of Alkynes

Although the hydroacylation reactions of simple alkynes will not generate new stereogenic centers on the alkyne moiety, nevertheless, the asymmetric intramolecular hydroacylation reactions of alkynes have emerged by applying either kinetic resolution or a desymmetrization strategy. 

In their previous study, the Fu group had demonstrated that Rh/(R)-Tol-BINAP was not effective for the kinetic resolution of 4-alkynals 54a-54c, providing a poor mass balance of unreacted 4-alkynals and cyclopentenones. However, a careful examination of the reaction mixture revealed that unexpected cyclobutanones 58 were generated in good yields and enantiomeric 

Meanwhile, the Fu group discovered the matched or mismatched nature of the catalyst versus the substrate eonfiguration (Seheme 8.27). When enan-tiopure 54a was treated with Rh catalysts derived from (R)-or (5)-Tol-BINAP, very different results were observed. In the case of (R)-Tol-BINAP, cyclobutanone 58a was obtained preferentially. For (S)-Tol-BINAP, cyclopentenone 55a was produced with exeellent selectivity. Therefore, simply by choosing the suitable enantiomer of the ligand, one can dictate which product is formed. 

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Scheme 8.28 Asymmetric hydroacylation reactions of alkynes reported by Willis.

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