Visible-Light-Promoted Three-Component Coupling Annulation: Synthesis of 2-Iminothiazolidin-4-ones via in Situ Formed Electron Donor–Acceptor Complexes

Abstract

A novel and efficient three-component coupling annulation strategy for the synthesis of 2-iminothiazolidin-4ones from amines, isothiocyanates, and alkyl acetylenedicarboxylates under visible-light irradiation conditions has been demonstrated. In this transformation, the in situ formed photoactive electron donor−acceptor (EDA) complexes facilitate the reaction and smoothly generate the corresponding products with a high adaptability under mild conditions. This protocol provides a cost-efficient and practical route to 2-iminothiazolidin-4-ones and promotes potential applications on the synthetic drugs.

Progress in Photoinduced Radical Reactions using Electron Donor‐Acceptor Complexes

“…Finally, an ammonolysis/cyclization process produces the desired product. In 2019, we further reported a similar three‐component coupling annulation strategy for the construction of 2‐iminothiazolidin‐4‐ones containing an unsaturated ester group under visible‐light irradiation conditions [36] . The established novel EDA complexes 353 from amines and isothiocyanates as electron donors and alkyl acetylenedicarboxylates 352 as electron acceptors promote the reaction process (Scheme 71).…”

“…Although the contributions of photocatalyzed synthesis of indolines and 2,3‐dihydrobenzofurans, these approaches were performed using Ir and Ru based complexes as photocatalysts [16,165] . In this context, the advantage of the EDA complex is considered to be an alternative for the synthesis of heterocyclic compounds [35–37] . Paixão et al developed a visible light‐induced intramolecular radical cyclization strategy for the synthesis of highly substituted indolines and 2,3‐dihydrobenzofurans under mild reaction conditions in good to excellent yields (Scheme 52).…”

“…In 2019, we further reported a similar threecomponent coupling annulation strategy for the construction of 2-iminothiazolidin-4-ones containing an unsaturated ester group under visible-light irradiation conditions. [36] The established novel EDA complexes 353 from amines and isothiocyanates as electron donors and alkyl acetylenedicarboxylates 352 as electron acceptors promote the reaction process (Scheme 71). These easily available and diverse functionalized 2-iminothiazolidin-4-ones may be applied in medicinal chemistry.…”

“…[16,165] In this context, the advantage of the EDA complex is considered to be an alternative for the synthesis of heterocyclic compounds. [35][36][37] Paixão et al developed a visible light-induced intramolecular radical cyclization strategy for the synthesis of highly substituted indolines and 2,3-dihydrobenzofurans under mild reaction conditions in good to excellent yields (Scheme 52). [166] The reaction occurs promoted by an EDA complex from N-ally-2-haloanilines and tris(trimethylsilyl) silane (TTMSS) without the requirement of any transition metals and photocatalysts.…”

“…[34] Additionally, we also accomplished some important achievements in metal-/photocatalyst-free, photochemical synthesis of a wide range of N-heterocyclic com-pounds enabled by EDA complexes under mild reaction conditions. [35][36][37] Despite the above contributions about this interesting topic, this review highlights the recent advancements on the metal-/photocatalyst-free photoinduced radical addition reactions, radical borylations, reductive reactions, radical-radical cross-coupling reactions, degradation reactions and radical cascade cyclization via EDA complexes from 2013 to 2020, and exceeding 70 examples of reactions, synthetic applications and their mechanisms are discussed in detail including our recent advances.…”