title: Enantioselective Synthesis of Allenes by Catalytic Traceless Petasis Reactions.
abstract: Allenes are useful functional groups in synthesis as a result of their inherent chemical properties and established reactivity patterns. One property of chemical bonding renders 1,3-substituted allenes chiral, making them attractive targets for asymmetric synthesis. While there are many enantioselective methods to synthesize chiral allenes from chiral starting materials, fewer methods exist to directly synthesize enantioenriched chiral allenes from achiral precursors. We report here an asymmetric boronate addition to sulfonyl hydrazones catalyzed by chiral biphenols to access enantioenriched allenes in a traceless Petasis reaction. The resulting Mannich product from nucleophilic addition eliminates sulfinic acid, yielding a propargylic diazene that performs an alkyne walk to afford the allene. Two enantioselective approaches have been developed; alkynyl boronates add to glycolaldehyde imine to afford allylic hydroxyl allenes, and allyl boronates add to alkynyl imines to form 1,3-alkenyl allenes. In both cases, the products are obtained in high yields and enantioselectivities.
authors.affiliation: Center for Molecular Discovery, Department of Chemistry, Boston University , 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States.
authors.forename: Yao
authors.identifier: 0000-0002-6137-1126
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Abdallah B
authors.initials: AB
authors.lastname: Diagne
authors.affiliation: Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Regan J
authors.identifier: 0000-0001-5546-4038
authors.initials: RJ
authors.lastname: Thomson
authors.affiliation: Center for Molecular Discovery, Department of Chemistry, Boston University , 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States.
authors.forename: Scott E
authors.initials: SE
authors.lastname: Schaus
mesh_terms: D000466:Alkadienes / Q000138:chemical synthesis* / Q000737:chemistry; D001897:Boronic Acids / Q000737:chemistry*; D002384:Catalysis; D006835:Hydrazones / Q000737:chemistry*; D015394:Molecular Structure; D010636:Phenols / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000466:Alkadienes; D001897:Boronic Acids; D006835:Hydrazones; D010636:Phenols