title: Ruthenium-catalyzed reductive coupling of 1,3-enynes and aldehydes by transfer hydrogenation: anti-diastereoselective carbonyl propargylation.
abstract: Under the conditions of ruthenium-catalyzed transfer hydrogenation employing isopropanol as a source of hydrogen, isopropoxy-substituted enyne 1 b and aldehydes 3 a-3 l engage in reductive coupling to provide products of propargylation 4 a-4 l with good to complete levels of anti-diastereoselectivity. The unprotected tertiary hydroxy moiety of isopropoxy enyne 1 b is required to enforce diastereoselectivity. Deuterium-labeling studies corroborate reversible enyne hydrometalation in advance of carbonyl addition. As demonstrated in the conversion of 4 f-h and 4 k to 5 f-h and 5 k, the isopropoxy group of the product is readily cleaved upon exposure to aqueous sodium hydroxide to reveal the terminal alkyne.
authors.affiliation: Department of Chemistry & Biochemistry, The University of Texas at Austin, 78712-1167, USA.
authors.forename: Laina M
authors.initials: LM
authors.lastname: Geary
authors.forename: Joyce C
authors.initials: JC
authors.lastname: Leung
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Krische
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D000480:Alkynes / Q000138:chemical synthesis* / Q000737:chemistry*; D002384:Catalysis; D006865:Hydrogenation; D015394:Molecular Structure; D010084:Oxidation-Reduction; D020005:Propanols / Q000138:chemical synthesis* / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000447:Aldehydes; D000480:Alkynes; D020005:Propanols; D012428:Ruthenium; C028255:propargyl alcohol