Dearomative Michael addition involving enals and 2-nitrobenzofurans realized under NHC-catalysis

Dearomative, aminocatalytic formal normal-electron-demand aza-Diels-Alder cycloaddition in the synthesis of tetrahydrofuropyridines

In the manuscript the application of dearomative formal normal-electron-demand aza-Diels-Alder cycloaddition in the synthesis of tetrahydrofuropyridines is described. The developed approach utilizes aminocatalytic activation of 2-alkyl-3-furfurals that proceeds via formation of the dearomatized dienamine intermediate. Initially obtained cycloadducts have been subjected to subsequent transformations providing access to tetrahydrofuropyridines or functionalized cinnamates. The mechanism of the process has been confirmed by DFT calculations.

Direct Access to 3-Thioether-Substituted Dihydrofuro[2,3-b]benzofurans via Tandem Reactions of Sulfur Ylides and 2-Nitrobenzofurans

The synthesis of 3-thioether-substituted dihydrofuro[2,3-b]benzofurans involving the [3 + 2] coupling of sulfur ylides with 2-nitrobenzofurans has been realized in moderate to good yields under mild conditions without any precious catalysts or additives. It is worth mentioning that the reutilization of the departed nitro-anion in the reaction process facilitates this new chemical transformation and presents a manner of high atom economy to provide products with a complex structure.

Multistep Cascade Catalytic Reactions Employing Bifunctional Framework Compounds

Multistep cascade reactions are important to achieve atom as well as step economy over conventional synthesis. This approach, however, is limited due to the incompatibility of the available reactive centers in a catalyst. In the present study, new MOF compounds, [Zn₂(SDBA)(3-ATZ)₂]·solvent, I and II, with tetrahedral Zn centers as good Lewis acidic sites and the free amino group of the 3-amino triazole ligand as a strong Lewis base center were shown to perform 4-step cascade/tandem reaction in a facile manner. Effective conversion of benzaldehyde dimethyl acetal in the presence of excess nitromethane at 100 °C in water to 1-(1,3-dinitropropan-2-yl) benzene was achieved in 10 h with yields of ∼95% (I) and ∼94% (II). This 4-step cascade reaction proceeds via deacetalization (Lewis acid), Henry (Lewis base), and Michael (Lewis base) reactions. The present work highlights the importance of spatially separated functional groups in multistep tandem catalysis─the examples of which are not common.

Photoredox Catalyzed Thioformylation of Terminal Alkynes Using Nitromethane as a Formyl Source

A photoredox thioformylation of terminal alkynes using nitromethane as a formyl anion equivalent, thereby leading to the synthesis of (E)-1,2-difunctionalized acrylaldehyde, has been described. The current strategy introduces an adaptable aldehyde function across an alkyne and offers a new route to synthesizing α-alkyl/aryl aldehydes.