Visible light-mediated aza Paternò-Büchi reaction of acyclic oximes and alkenes to azetidines

The aza Paternò-Büchi reaction is a [2+2]-cycloaddition reaction between imines and alkenes that produces azetidines, four-membered nitrogen-containing heterocycles. Currently, successful examples rely primarily on either intramolecular variants or cyclic imine equivalents. To unlock the full synthetic potential of aza Paternò-Büchi reactions, it is essential to extend the reaction to acyclic imine equivalents. Here, we report that matching of the frontier molecular orbital energies of alkenes with those of acyclic oximes enables visible light-mediated aza Paternò-Büchi reactions through triplet energy transfer catalysis. The utility of this reaction is further showcased in the synthesis of epi-penaresidin B. Density functional theory computations reveal that a competition between the desired [2+2]-cycloaddition and alkene dimerization determines the success of the reaction. Frontier orbital energy matching between the reactive components lowers transition-state energy (ΔGǂ) values and ultimately promotes reactivity.

Synthesis and in vitro anticancer activity of penaresidin-related stereoisomeric analogues

A straightforward route to penaresidin-based derivatives with an unsubstituted alkyl side chain was developed. To construct these stereoisomeric azetidene-derived alkaloids, [3,3]-sigmatropic rearrangements followed by late stage olefin cross metathesis and an intramolecular nucleophilic type substitution were involved as the key transformations. The protected d-ribofuranose was chosen as the sole chiral source. The ability of target molecules to inhibit cancer cells proliferation was evaluated on a panel of five malignant cell lines.

Synthesis of polysubstituted azetidines via cascade trifluoromethylation/cyclization of N-allyl ynamides

A cascade trifluoromethylation/cyclization of N-allyl sulfonylynamides is developed, providing a direct access to azetidine-fused tricyclic compounds at room temperature.

NHC catalyzed enantioselective Coates-Claisen rearrangement: a rapid access to the dihydropyran core for oleuropein based secoiridoids

A simple protocol for the synthesis of the dihydropyran core structure of secoiridoids using NHC catalyzed Coates-Claisen rearrangement is described.

Square sugars: challenges and synthetic strategies

The synthesis of square sugars requires innovative strategies based on efficient stereoselective methodologies, from organocatalysis to metal carbene insertion.

An efficient Sn(ii)-catalyzed one-pot synthesis of a 3-substituted azetidine-2,4-dione framework

A novel Sn(ii)-catalyzed tandem cyclization reaction of aromatic aldehydes with ethyl cyanoacetate has been achieved to afford a series of 3-substituted azetidine-2,4-diones in good to excellent yields.