Molecular gymnastics of alkynes orchestrated by ruthenium complexes

Ruthenium complexes catalyze a variety of addition or isomerization reactions that are highly atom economical. Terminal alkynes react with allyl alcohols to form beta,gamma-unsaturated ketones that can be readily isomerized to alpha,beta-unsaturated ketones via transient vinylidene complexes. A cyclization via a transient allenylidene complex concomitant with this addition represents a novel way to build heterocycles. Ancillary studies with these catalysts revealed an internal oxidation reduction ketones and propargyl alcohols are isomerized to alpha,beta-unsaturated carbonyl compounds. Consideration of the reaction whereby allyl alcohols are isomerized to saturated rated carbonyl compounds. Consideration of the reaction mechanism led to a general Alder ene type reaction wherein alkynes serve as the enophile and alkenes serve as the ene component. These discoveries have led to a number of efficient total syntheses of biologically interesting targets. Mechanistic investigations into the activation of a ruthenium complex led to the discovery of a novel bis-homo-Diels-Alder reaction of 1,4-cyclooctadiene.