Iridium-Catalyzed Enantioselective Ring Opening of Alkenyl Oxiranes by Unactivated Carboxylic Acids

An iridium-catalyzed enantioselective ring-opening of alkenyl oxiranes by unactivated carboxylic acids has been developed. The reaction undergoes at ambient conditions between an in-situ-generated chiral iridium-π-allyl complex and carboxylic acids to provide rapid access to valuable alkenyl diols in high yields. The synthetic utility of this method is demonstrated by the elaboration of the products into various medium and large ring-sized compounds that are part of biologically relevant molecules.

Copper-catalyzed S-arylation of Furanose-Fused Oxazolidine-2-thiones

The 1,3-oxazolidine-2-thiones (OZTs) are important chiral molecules, especially in asymmetric synthesis. These compounds serve as important active units in biologically active compounds. Herein, carbohydrate anchored OZTs were explored to develop a copper-catalyzed C-S bond formation with aryl iodides. Chemoselective S-arylation was observed, with copper iodide and dimethylethylenediamine (DMEDA) as the best ligand in dioxane at 60–90 °C. The corresponding chiral oxazolines were obtained in reasonable to good yields under relatively mild reaction conditions. This approach is cheap, as using one of the cheapest transition metals, a simple protocol and various functional group tolerance make it a valuable strategy for getting S-substituted furanose-fused OZT. The structures of the novel carbohydrates were confirmed by NMR spectroscopy and an HRMS analysis.

Access to Fused Tricyclic γ-Butyrolactones, A Natural Product-like Scaffold

Serendipitous findings of an acid mediated skeletal rearrangement of bicyclo-β-ketoester having cyclopropyl ring to access fused tricyclic γ-butyrolactones has been described. This novel transformation has been optimized to 30 mol% p-toluenesulfonic acid (p-TSA) in toluene using Dean-Stark apparatus, where the aldol condensation, cyclopropyl ring opening followed by cyclization took place in a single-pot operation. The resulting tricyclic compounds are interesting chemotype with natural product resemblance and may find useful applications in the future.