title: Highly enantioselective reductive cyclization of acetylenic aldehydes via rhodium catalyzed asymmetric hydrogenation.
abstract: Catalytic hydrogenation of acetylenic aldehydes 1a-12a using chirally modified cationic rhodium catalysts enables highly enantioselective reductive cyclization to afford cyclic allylic alcohols 1b-12b. Using an achiral hydrogenation catalyst, the chiral racemic acetylenic aldehydes 13a-15a engage in highly syn-diastereoselective reductive cyclizations to afford cyclic allylic alcohols 13b-15b. Ozonolysis of cyclization products 7b and 9b allows access to optically enriched alpha-hydroxy ketones 7c and 9c. Reductive cyclization of enyne 7a under a deuterium atmosphere provides the monodeuterated product deuterio-7b, consistent with a catalytic mechanism involving alkyne-carbonyl oxidative coupling followed by hydrogenolytic cleavage of the resulting oxametallacycle. These hydrogen-mediated transformations represent the first examples of the enantioselective reductive cyclization of acetylenic aldehydes.
authors.affiliation: University of Texas at Austin, Department of Chemistry and Biochemistry, Austin, Texas 78712, USA.
authors.forename: Jong Uk
authors.initials: JU
authors.lastname: Rhee
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Krische
mesh_terms: D000114:Acetylene / Q000737:chemistry*; D000447:Aldehydes / Q000737:chemistry*; D002384:Catalysis; D015394:Molecular Structure; D012238:Rhodium / Q000737:chemistry*
chemical_list: D000447:Aldehydes; D012238:Rhodium; D000114:Acetylene