Zur 1.3-dipolaren cycloaddition aromatischer nitriloxide an azodicarbonsäureester

A facile tertiary amine-mediated [2+2] annulation reaction of 3-alkyl allenoates, and diaryl 1,2-diones leading to diastereoselective synthesis of highly substituted alkylene-oxetane derivatives is reported. The reaction was further extended to α-ketoamides. The obtained amide-appended oxetanes were transformed to 5-methylene-1H-pyrrol-2(5H)-one derivatives with potential biological activity.

A novel annulation reaction of trans-2-substituted-3-nitrocyclopropane-1,1-carboxylates with in situ generated Huisgen zwitterions is reported, providing facile synthesis of 3-alkoxy pyrazolines in good yields and high diastereoselectivities. This reaction unveils the divergent reactivity of the nitrocyclopropanes as a kind of versatile donor–acceptor cyclopropanes. It is also demonstrated that the prepared 3-alkoxy pyrazolines from di-tert-butyl azodicarboxylate can be readily transformed into the corresponding 3-alkoxy 1H-pyrazoles in moderate yields.

A novel annulation reaction of 3-acylmethylidene oxindoles with Huisgen zwitterions is unveiled that leads to an unprecedented synthetic method for complex pyrrolo­[4,3,2-de]­quinolinones and marine alkaloids ammosamides A–C. This method features simplicity, high efficiency, and broad substrate scope and is accordingly anticipated to significantly facilitate the preparation and bioassay of the relevant pyrroloquinoline alkaloids and their analogues.

Novel spirooxindole-pyrazolines and spirobenzofuranone-pyrazolines have been synthesized in good to excellent yields via the annulation reactions of the corresponding 3-alkylideneoxindoles and 3-alkylidenebenzofuranones with Huisgen zwitterions. The preliminary bioassay demonstrated that some of the spiropyrazolines possess good in vitro fungicidal activity against several crop fungi at a concentration of 50 μg mL⁻¹.

The nitrogen-based nucleophile generated from azodicarboxylate and triphenylphosphine displayed good reactivity toward benzofuran-2,3-diones to generate a variety of spirocyclic benzofuran-2-one derivatives. The reactions accommodate a number of benzofuran-2,3-diones and different dialkylazodicarboxylates to give the enriched functionalized 3-spirooxadiazole benzofuran-2-ones with moderate to good yields (up to 93%).

An efficient synthesis of aryliminophosphoranes is described. A mixture of an aromatic amine, diethyl azodicarboxylate and triphenylphosphine undergo a Mitsonobu type reaction at ambient temperature in dry dichloromethane to afford aryliminophosphoranes in excellent yields.