Lewis Acid-Catalyzed Synthesis of Polysubstituted Furans from Conjugated Ene-yne-ketones and 1,3,5-Triazinanes

Abstract

An efficient and metal-free approach to the construction of diverse functionalized furan derivatives has been developed from ene-yne-ketones and 1,3,5-triazinanes. As an atomeconomical and environment-friendly protocol, the new conditions are suitable for selective C−N and C−O bond formation of a wide range of polysubstituted furans in one pot.

Structural and Dynamic Behaviour of Heterocycles Derived from Ethylenediamines with Formaldehyde: 1,3,5-Triazinanes and Bis(imidazolidinyl)methanes

“…In order to explore the versatility of formaldehyde in the synthesis of other six-membered heterocycles, the reactions of N-benzyl-amine in the presence of formaldehyde and sodium hydrosulphide in different proportions were explored. The equimolar reaction between N-benzylamine and formaldehyde led exclusively to the formation of N-benzyltriazinane (3, 98% yield), which has already been previously reported by other research groups under different reaction conditions [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44]. The reaction of one equivalent of Nbenzylamine with five of formaldehyde and three of sodium hydrosulphide was explored, obtaining a mixture of products in 50:50 ratios: N-benzyl-thiadiazinane (4) and Nbenzyl-dithiazinane (5).…”

Accessing Functionalized Furans from Reacting Enynones and Enynals through Furyl Metal Carbenes

“…In 2022, the Zhu and Cao group accomplished Lewis acidcatalyzed alkyne activation to facilitate intramolecular 5-exo-dig cyclization of enynones (Scheme 34). [48] Utilizing BF 3 •OEt 2 , enynones 1, and 1,3,5-triazines 90, furyl amines 91 were synthesized via CÀ N bond formation, demonstrating a wide substrate scope and good functional group tolerance. The reaction process involves the activation of the alkyne moiety of enynone 1 by BF 3 •OEt 2 , leading to the formation of zwitterionic intermediate I. Aziridination then proceeds with 90', derived from 90, to form aziridine intermediate II.…”

Synthesis of Polysubstituted Furans: An Update Since 2019

“…For the construction of multisubstituted furans, [116][117] Zhu et al in 2022 disclosed a one-pot metal-free Lewis-acid catalyzed synthesis of substituted furans 227 from conjugated eneyne-ketones 220 and 1,3,5-triazinanes 221 in good to excellent yields. [118] The mechanism proceeds with the activation of 220 by the BF The corresponding furan derivatives were produced in good to excellent yields by EDGs such as À Me, À OMe, -t Bu, À Br, À SMe and À Ph at para or meta position. Lower product formation efficiency was caused by substrates having EWGs including À F, À Cl, À CF 3 , À OCF 3 , and À COOCH 3 at the aryl ring (Scheme 30).…”

“…For the construction of multisubstituted furans, [116–117] Zhu et al. in 2022 disclosed a one‐pot metal‐free Lewis‐acid catalyzed synthesis of substituted furans 227 from conjugated ene‐yne‐ketones 220 and 1,3,5‐triazinanes 221 in good to excellent yields [118] . The mechanism proceeds with the activation of 220 by the BF 3 .OEt 2 catalyst which is used for the intramolecular nucleophilic attack of carbonyl oxygen to afford intermediate 223 .…”