title: Asymmetric formal trans-dihydroxylation and trans-aminohydroxylation of alpha,beta-unsaturated aldehydes via an organocatalytic reaction cascade.
abstract: This study demonstrates the first formal asymmetric trans-dihydroxylation and trans-aminohydroxylation of alpha,beta-unsaturated aldehydes in an organocatalytic multibond forming one-pot reaction cascade. This efficient process converts alpha,beta-unsaturated aldehydes into optically active trans-2,3-dihydroxyaldehydes and trans-3-amino-2-hydroxyaldehydes with the aldehyde moiety protected as an acetal. The elaborated one-pot protocol proceeds via the formation of 2,3-epoxy and 2,3-aziridine aldehyde intermediates, which subsequently participate in a novel NaOMe-initiated rearrangement reaction leading to the formation of acetal protected trans-2,3-dihydroxyaldehydes and trans-3-amino-2-hydroxyaldehydes in a highly stereoselective manner. Advantageously, this multibond forming reaction cascade can be performed one-pot, thereby minimizing the number of manual operations and purification procedures required to obtain the products. Additionally, for the purpose of trans-aminohydroxylation of the alpha,beta-unsaturated aldehydes, a new enantioselective aziridination protocol using 4-methyl-N-(tosyloxy)benzenesulfonamide as the nitrogen source has been developed. The mechanism of the formal trans-dihydroxylation and trans-aminohydroxylation of alpha,beta-unsaturated aldehydes is elucidated by various investigations including isotopic labeling studies. Finally, the products obtained were applied in the synthesis of numerous important molecules.
authors.affiliation: Center for Catalysis, Department of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark.
authors.forename: Łukasz
authors.initials: Ł
authors.lastname: Albrecht
authors.forename: Hao
authors.initials: H
authors.lastname: Jiang
authors.forename: Gustav
authors.initials: G
authors.lastname: Dickmeiss
authors.forename: Björn
authors.initials: B
authors.lastname: Gschwend
authors.forename: Signe Grann
authors.initials: SG
authors.lastname: Hansen
authors.forename: Karl Anker
authors.initials: KA
authors.lastname: Jørgensen