Three-Component Condensation of Pyridinium Ylides, β-Ketonitriles, and Aldehydes with Divergent Regioselectivity: Synthesis of 4,5-Dihydrofuran-3- and 2H-Pyran-5-carbonitriles

Annulation of a Methylenecyclopropane with Cyanoalkenes Catalyzed by Lewis Bases

The annulation of a methylenecyclopropane with acyl cyanoalkenes by using DABCO or quinuclidine as a catalyst to give 2,3-dihydofurans has been developed. A stoichiometric amount of the Lewis bases promoted the isomerization of 2,3-dihydrofurans to furans. 1 H NMR spectra of the reaction in situ revealed that the methylenecyclopropane is opened by the Lewis base to form a reaction intermediate that is added to the cyanoalkenes.

Three-Component Condensation of β-Ketonitriles, 4-Fluorobenzaldehyde, and Secondary Cyclic Amines

A new three-component condensation of β-ketonitriles, 4-fluorobenzaldehyde, and secondary cyclic amines was developed. A possible reaction mechanism has been proposed including Knoevenagel condensation followed by aromatic nucleophilic substitution. It was found that in the case of 3-oxopropanenitrile bearing the 6-amino-1,3-dimethyluracil moiety, the reaction is not accompanied by fluorine substitution in the Knoevenagel adduct, and the Michael addition of a secondary amine occurs followed by oxidation.

Electrochemical Aerobic Oxygenation and Nitrogenation of Cyclic Alkenes via C═C Bond Cleavage or Oxygenation and Azidation of Open-Chain Alkenes

An efficient strategy involving electrochemical C═C double-bond cleavage and functionalization of cyclic alkenes for the synthesis of ketonitriles is described. This transformation features environmentally friendly conditions and utilizes relatively safe TMSN₃ as the nitrogenation reagent and molecular oxygen as the oxidant. For the open-chain alkenes, the reaction gave 1,2-difunctionalized products. A wide range of cyclic alkenes and open-chain alkenes were found to be compatible, providing the corresponding ketonitriles and α-azido aromatic ketones in moderate to good yields.

Efficient synthesis of tetra- and penta-substituted benzenes via a domino annulation reaction of a pyridinium ylide and chalcone o-enolate

A very simple and highly efficient protocol for synthesizing tetra- and penta-substituted benzene derivatives has been developed.