Platinum-Catalyzed α,β-Desaturation of Cyclic Ketones through Direct Metal-Enolate Formation

The development of a platinum-catalyzed desaturation of cyclic ketones to their conjugated alpha,beta-unsaturated counterparts is reported in this full article. A unique diene-platinum complex was identified to be an efficient catalyst, which enables direct metal-enolate formation. The reaction operates under mild conditions without using strong bases or acids. Good to excellent yields can be achieved for diverse and complex scaffolds. A wide range of functional groups, including those sensitive to acids, bases/nucleophiles, or palladium species, are tolerated, which represents a distinct feature from other known desaturation methods. Mechanistically, this platinum catalysis exhibits a fast and reversible alpha-deprotonation followed by a rate-determining beta-hydrogen elimination process, which is different from the prior Pd-catalyzed desaturation method. Promising preliminary enantioselective desaturation using a chiral-diene-platinum complex has also been obtained.

Automated summary

This article describes a platinum-catalyzed desaturation of cyclic ketones to their conjugated alpha,beta-unsaturated counterparts, which operates under mild conditions without the need for strong bases or acids. The method shows good functional group tolerance and can be applied to diverse and complex structures. The mechanism involves fast and reversible alpha-deprotonation followed by a rate-determining beta-hydrogen elimination process, distinguishing it from prior palladium-catalyzed methods.