A Diastereoselective Synthesis of β‐(N‐Acylamino)aldehydes by Rearrangement of O‐Vinyl‐N,O‐Acetals

Generation and Rearrangement of N,O‐Dialkenylhydroxylamines for the Synthesis of 2‐Aminotetrahydrofurans

“…[17] In contrast, we anticipated that mild basic conditions might cleave the tetrahydrofuran C À Ob ond and convert 8 to highly-substituted cyclopentanone products via af ormal aza-Petasis-Ferrier rearrangement. [18] Gratifyingly,t reatment of 8a with MeI in the presence of K 2 CO 3 ,resulted in tetrahydrofuran ring-opening, alkylation, and Mannich addition to form b-amino-cyclopentenone 9a with high diastereoselectivity (Scheme 4). The preferred conformation of this product was confirmed by Xray crystallography.…”

Asymmetric Organocatalytic Rearrangement Reactions

“…[35] This interesting reaction proceeds through C À O bond cleavage of a hemiaminal vinyl ether by the action of an acid catalyst, to afford a reactive iminium cation and the enol form of an aldehyde; these two intermediates combine subsequently in a Mannich-type process, leading to b-amino aldehydes (Scheme 11). [36] After developing a straightforward synthesis of the requisite hemiaminal vinyl ethers by the Ni II -catalyzed isomerization of the readily available hemiaminal allyl ethers (Scheme 12), these authors found that the rearrangement could be efficiently catalyzed by means of the BINOL-derived phosphoric acid diester (R)-16 (Table 14). Due to the instability of the resulting aldehydes, these were subsequently reduced to the corresponding g-amino alcohols.…”

The [1, 3] O-to-C rearrangement: opportunities for stereoselective synthesis

“…Frauenrath and coworkers were the first to report this reactivity and showed that sterics will override the stereochemical influence of enolate geometry (eqn 23). 48 The allyl group also provides sufficient electron donation to fragment allyl vinyl ethers in the presence of a Lewis acid. The corresponding ion pair allows access to the [1, 3] product in the face of a possible [3, 3] rearrangement.…”