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Updated: Jul 12, 2025
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Published on: June 21, 2017
Asymmetric Ruthenium-Catalyzed Carbonyl Allylations by Gaseous Allene via Hydrogen Auto-Transfer: 1° vs 2° Alcohol
Connor Saludares1, Eliezer Ortiz1, Cate G Santana1
1University of Texas at Austin, Department of Chemistry, 105 E 24th St. Austin, TX 78712, USA.
Abstract:
Iodide-bound ruthenium-JOSIPHOS complexes catalyze the redox-neutral C-C coupling of primary alcohols 2a-2r with the gaseous allene (propadiene) 1a to form enantiomerically enriched homoallylic alcohols 3a-3r with complete atom-efficiency. Using formic acid as reductant, aldehydes dehydro-2a and dehydro-2c participate in reductive C-C coupling with allene to deliver adducts 3a and 3c with comparable levels of asymmetric induction. Deuterium labeling studies corroborate a mechanism in which alcohol dehydrogenation triggers allene hydroruthenation to form transient allylruthenium-aldehyde pairs that participate in carbonyl addition. Notably, due to a kinetic preference for primary alcohol dehydrogenation, chemoselective C-C coupling of 1°,2°-1,3-diols occurs in the absence of protecting groups. As illustrated by the synthesis of C7-C15 of spirastrellolide B and F (7 vs 17 steps), C3-C10 of cryptocarya diacetate (3 vs 7 or 9 steps), and a fragment common to C8'-C14' of mycolactone F (1 vs 4 steps) and C22-C28 marinomycin A (1 vs 9 steps), this capability streamlines type I polyketide construction.
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