Enantioselective transformations of 5-hydroxymethylfurfural via catalytic asymmetric 1,3-dipolar cycloaddition of azomethine ylides

Metal catalyzed asymmetric 1,3-dipolar cycloaddition of azomethine ylides: structural diversity at the dipole partner

The 1,3-dipolar cycloaddition of azomethine ylides represents a versatile approach for synthesizing pyrrolidines, valuable structural motifs in synthetic and medicinal chemistry. However, most studies to date have relied predominantly on α-iminoesters as ylide precursors, thereby limiting the broader synthetic applications of this strategy. This feature article highlights alternative azomethine ylide precursors, beyond conventional α-iminoesters, which have facilitated the preparation of pyrrolidines with new subtitution patterns.

Unnatural Cyclopeptide Synthesis via Cu-Catalyzed 1,3-Dipolar Cycloaddition of Azomethine Ylides

Cyclic peptides are valued synthetic targets in organic and medicinal chemistry. Herein, we report an efficient strategy for the synthesis of unnatural cyclic peptides via the Cu-catalyzed 1,3-dipolar cycloaddition of azomethylene ylides. Linear precursors of different lengths and bearing diverse amino acids (26 examples) are shown to be compatible with this method, affording good yields and complete endo-diastereoselectivities. Density functional theory (DFT) calculations support a stepwise mechanism in which Cu plays a key role in the preorganization of the reactants.

Atroposelective Synthesis of Axially Chiral Naphthylpyrroles by a Catalytic Asymmetric 1,3-Dipolar Cycloaddition/Aromatization Sequence

A straightforward methodology for the enantioselective preparation of axially chiral 2-naphthylpyrroles has been developed. This protocol is based on a CuI/Fesulphos-catalyzed highly enantioselective 1,3-dipolar cycloaddition of an azomethine ylide followed by pyrrolidine alkylation and pyrrolidine to pyrrole oxidation. The mild conditions employed in the DDQ/blue light-mediated aromatization process facilitate an effective central-to-axial chirality transfer affording the corresponding pyrroles with high atroposelectivity.

Dipolarophile-Steered Formal Stereodivergent Synthesis of 2,5-cis/trans-Pyrrolidines Based on Asymmetric 1,3-Dipolar Cycloaddition of Imino Lactones

The stereodivergent asymmetric synthesis of 2,5-trans/cis pyrrolidines by 1,3-dipolar cycloaddition using two different types of activated alkenes is described. When ylidene-isoxazolones were employed as dipolarophiles, the Ag/(S,Sp )-iPr-FcPHOX-catalyzed asymmetric [3+2] cycloaddition of imino lactones proceeded with 2,5-trans selectivity. Subsequent decarboxylation of the isoxazolone rings produced pyrrolidines with 2,5-trans stereoretention. In the reaction using acyclic enones as activated alkenes, the Ag/(R,Sp )-ThioClickFerrophos complex-catalyzed asymmetric [3+2] cycloaddition afforded 2,5-cis substituted pyrrolidines in high yields and enantioselectivities. Therefore, these methods can be considered as a formal stereodivergent synthesis of 2,5-cis/trans pyrrolidines.