Synergistic Catalysis for the Asymmetric [3+2] Cycloaddition of Vinyl Aziridines with α,β-Unsaturated Aldehydes
Line Naesborg1, Fernando Tur1, Marta Meazza1
1Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark.
Abstract:
The first asymmetric [3+2] cycloaddition of vinyl aziridines with α,β-unsaturated aldehydes, based on synergistic catalysis, is disclosed. This methodology allows the formation of attractive pyrrolidine structures in good yields (up to 84 %), moderate diastereoselectivity, and high enantioselectivity values (up to >99 % ee). Additionally, a tricyclic pyrrolidine core structure found in biologically active molecules was synthesized in a one-pot fashion by using the presented reaction concept. Finally, a mechanistic proposal is outlined.
Related Concept Videos
Cycloaddition Reactions: Overview
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
[3,3] Sigmatropic Rearrangement of Allyl Vinyl Ethers: Claisen Rearrangement
Conjugate Addition to α,β-Unsaturated Carbonyl Compounds
Cycloaddition Reactions: MO Requirements for Thermal Activation
Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.


