Isolable Gold(I) Complexes Having One Low-Coordinating Ligandas Catalysts for the Selective Hydration of Substituted Alkynes atRoom Temperature without Acidic Promoters

摘要

Hydration of a wide range of alkynes to the corresponding ketones has been afforded in high yields atroom temperature by using gold(I)—phosphine complexes as catalyst, with no acidic cocatalysts required.Suitable substrates covering alkyl and aryl terminal alkynes, enynes, internal alkynes, and propargylicalcohols, including enantiopure forms, are cleanly transformed to the corresponding ketones in nearlyquantitative yields. Acid-labile groups present in the substrates are preserved. The catalytic activity stronglydepends on both the nature of the phosphine coordinated to the gold (I) center and the softness of thecounteranion, the complex AuSPhosNTf2 showing the better activity. A plausible mechanism for thehydration of alkynes through ketal intermediates is proposed on the basis of kinetic studies. The describedcatalytic system should provide an efficient alternative to mercury-based methodologies and be useful insynthetic programs.