A New Mode of Cyclization of Enynes: Synthesis of Cycloalkyl Ketones through a Platinum-Catalyzed Hydrative Cycloisomerization Reaction

A new platinum-catalyzed cascade reaction that proceeds through an unusual cyclization pathway of enyne derivatives is described. This operationally simple, air-and moisture-tolerant reaction affords cycloalkyl ketone derivatives in a straightforward manner. The reaction can be considered as an unprecedented abnormal platinum-catalyzed cyclization of enynes. The role of the platinum catalyst promoting at least three different reactions in this auto-tandem catalytic process should also be remarked. The reaction also includes an unusual site-selective hydration of a practically symmetrical carbon-carbon triple bond directed by a hydroxy group. In this work we also describe the first platinum-catalyzed intramolecular hydroalkylation of an unactivated olefin with a simple dialkyl ketone.