Combining two-directional synthesis and tandem reactions: desymmetrisation by intramolecular cycloaddition/triazoline fragmentation

Metal-free Three-Component Synthesis of 1,2,3-Triazoline-4-sulfonamides

A new type of diazo compounds, namely, CH-diazomethane sulfonamides (generated in situ from readily available α-acetyl-α-diazomethane sulfonamides), was employed in a 1,3-dipolar cycloaddition reaction with imines (also formed in situ from primary amines and aldehydes). The reaction gave hitherto undescribed 1,5-disubstituted 1,2,3-triazoline-4-sulfonamides, which were obtained in good to excellent yields with complete trans diastereoselectivity. These new sulfonamides based on the nonaromatic 1,2,3-triazoline core are rather attractive from a medicinal chemistry standpoint in light of the strong emphasis recently put on the nonflat, more saturated (higher Fsp3) scaffolds for lead-generation libraries. The oxidative aromatization of 1,2,3-triazoline-4-sulfonamides by manganese(IV) oxide gave nearly quantitative yields of 1,2,3-triazole-4-sulfonamides, of which only two examples have been reported in the literature.

Metal-Free Three-Component Domino Approach to Phosphonylated Triazolines and Triazoles

An efficient, three-component domino reaction between aldehydes, amines, and the Bestmann-Ohira reagent is reported that enables a general, mild, and straightforward access to 1,4,5-trisubstituted 1,2,3-triazolines and triazoles. The reaction proceeds through a domino-condensation/1,3-dipolar cycloaddition sequence to afford the triazoline derivatives with excellent diastereoselectivity. Moreover, when both amine and aldehyde employed for this reaction are aromatic, a spontaneous oxidation afforded 1,4,5-trisubstituted triazoles in moderate yields.

Two-directional synthesis as a tool for diversity-oriented synthesis: Synthesis of alkaloid scaffolds

Two-directional synthesis represents an ideal strategy for the rapid elaboration of simple starting materials and their subsequent transformation into complex molecular architectures. As such, it is becoming recognised as an enabling technology for diversity-oriented synthesis. Herein, we provide a thorough account of our work combining two-directional synthesis with diversity-oriented synthesis, with particular reference to the synthesis of polycyclic alkaloid scaffolds.

An enantioselective desymmetrisation approach to C9-substituted trans-hydrindene rings based on a diastereotopic group-selective intramolecular Diels–Alder reaction

The synthesis of an achiral skipped bis(1,3-diene) substrate was achieved, which was shown to undergo an enantioselective, diastereotopic group-selective, intramolecular Diels-Alder reaction.

An expeditious stereoselective synthesis of natural (−)-Cassine via cascade HWE [3 + 2]-cycloaddition process

l-Rhamnose is transformed to (-)-Cassine via a remarkable four step one pot reaction. The Horner-Wadsworth-Emmons [3 + 2]-1,3-dipolar cycloaddition reaction cascade is the pivotal step in this reaction sequence and makes the synthesis highly efficient.