Enantioselective Vinylogous Conia-Ene Reaction Catalyzed by a Disilver(I)/Bisdiamine Complex

Green synthesis for diverse bioactive benzo-fused spiroindolines through DBU-catalysed post-Ugi double cyclization

A metal-free protocol utilizing DBU catalysis for post-Ugi amide-ester exchange and Conia-ene double cyclization has been successfully developed, allowing the synthesis of diverse highly functionalized benzo-fused spiroindolines with anti-cancer activities under mild conditions. Remarkably, this methodology demonstrates promising prospects for green chemistry, as it allows for the preparation of the spiroindolines in water. Control experiments indicate that a crucial role of the cyclic imide, specifically ring rigidification, facilitates the subsequent Conia-ene cyclization.

Electrophile-Controlled Regiodivergent Palladium-Catalyzed Imidoylative Spirocyclization of Cyclic Alkenes

An intermolecular controllable Pd-catalyzed spirocyclization of isocyano cycloalkenes has been developed, offering efficient and selective approaches toward spirocyclic hydropyrrole scaffolds. 2-Azaspiro-1,7-dienes could be obtained through a "chain-walking" process with aryl/vinyl iodides as electrophiles, while the normal Heck product 2-azaspiro-1,6-dienes were selectively generated when aryl triflates were used as the coupling partner of isocyanides. Mechanistic studies suggested that the counteranion of the Pd(II) intermediate played a crucial role in the regioselectivity control. Dihydropyrrole-fused 5,6,7-membered spirocycles were switchably accessed under mild conditions with wide functional group tolerance.

Green Synthesis of Spiro Compounds with Potential Anticancer Activity through Knoevenagel/Michael/Cyclization Multicomponent Domino Reactions Organocatalyzed by Ionic Liquid and Microwave-Assisted

In this work a microwave-assisted Knoevenagel/Michael/cyclization multicomponent domino methodology, using ethanol as solvent and the ionic liquid 1-methylimidazolium chloride as catalyst was developed for the synthesis of spiro compounds. The reaction conditions considered ideal were determined from a methodological study varying solvent, catalyst, amount of catalyst, temperature, and heating mode. Finally, the generality of the methodology was evaluated by exploring the scope of the reaction, varying the starting materials (isatin, malononitrile, and barbituric acid). Overall, the twelve spiro compounds were synthesized in good yields (43-98%) and the X-ray structure of compound 1b was obtained. In addition, the in vitro antiproliferative activities of the spirocycles against four types of human cancer cell lines including HCT116 (human colon carcinoma), PC3 (prostate carcinoma), HL60 (promyelocytic leukemia), and SNB19 (astrocytoma) were screened by MTT-based assay. It is noteworthy that spiro compound 1c inhibited the four cell lines tested with the lowest IC₅₀ values: 52.81 µM for HCT116, 74.40 µM for PC3, 101 µM for SNB19, and 49.72 µM for HL60.