Bifunctional phase-transfer catalysts for synthesis of 2-oxazolidinones from isocyanates and epoxides

Chiral bifunctional organocatalysts for enantioselective synthesis of 3-substituted isoindolinones

A series of chiral bifunctional organocatalysts were prepared and used for enantioselective synthesis of 3-substituted isoindolinones from 2-formylarylnitriles and malonates through aldol-cyclization rearrangement tandem reaction in excellent yields and enantioselectivites (up to 87% yield and 95% ee) without recrystallization. In this investigation, we found that chiral tertiary-amine catalysts with a urea group can afford 3-substituted isoindolinones both in higher yields (87% vs. 77%) and enantioselectivities (95% ee vs. 46% ee) than chiral bifunctional phase-transfer catalysts.

Efficient methods for the synthesis of chiral 2-oxazolidinones as pharmaceutical building blocks

Although the wide variety of heterocyclic compounds is common knowledge, chiral 2-oxazolidinones are recognized as some of the most important heterocycles in medicinal chemistry. Many important pharmaceutical molecules have been constructed based on the chiral 2-oxazolidinone backbone. Therefore, the development of even more efficient catalytic methods for the synthesis of chiral 2-oxazolidinones remains a very important pursuit in the field of synthetic organic chemistry. This review summarizes the coupling reactions of epoxides and isocyanates for the preparation of 2-oxazolidinones. Both metal catalysts and organocatalysts promote these reactions. Optically pure 2-oxazolidinones are prepared from optically pure epoxide substrates via these catalytic methods. A synthetic example of a commercially available pharmaceutical compound utilizing this method is also introduced.

Synthesis of Novel Crown Ether-Squaramides and Their Application as Phase-Transfer Catalysts

This work presents the synthesis of six new phase-transfer organocatalysts in which the squaramide unit is directly linked to the nitrogen atom of an aza-crown ether. Four chiral skeletons, namely hydroquinine, quinine, cinchonine (cinchonas), and α-d-glucopyranoside were responsible for the asymmetric construction of an all-carbon quaternary stereogenic center in α-alkylation and Michael addition reactions of malonic esters. We investigated the effects of these different chiral units and that of crown ethers with different sizes on catalytic activity and enantioselectivity. During extensive parameter investigations, both conventional and emerging green solvents were screened, providing valuable α,α-disubstituted malonic ester derivatives with excellent yields (up to 98%).