DBU-promoted tandem Michael-addition/cyclization for the synthesis of polysubstituted pyrroles

Recent Advances on Pyrrole Synthesis through Different Annulation Modes

“…In 2019, Hu group [81] described a 1,5-dizzabicyclo-[5.4.0]undecen-5-ene (DBU)-promoted method for the synthesis of pyrroles from α,β-unsaturated ynones and N-substituted ethyl glycine ethyl ester hydrochlorides in good yields (Scheme 49). This protocol is a transition-metal-free tandem Michael-addition/cyclization process, which shows advantages of mild reaction conditions, readily available starting materials and a wide scope of substrates.…”

Tandem Reactions of Ynones: via Conjugate Addition of Nitrogen‐, Carbon‐, Oxygen‐, Boron‐, Silicon‐, Phosphorus‐, and Sulfur‐Containing Nucleophiles

“…The NH 2 –Nu compounds– reacted with ynones to give cyclic components. Hydrazine, guanidine, hydroxylamine, o ‐phenylenediamines, and glycine ethyl ester hydrochlorides were applied in these transformations (Scheme ).…”

Novel synthesis of furancarboxylate derivatives via cyclization reactions of (E)-ethyl 3-aryl-2-cyanoacrylates and ethyl glycinate hydrochloride

“…Many studies have shown that glycinate derivatives are highly active and common intermediates in the synthesis of many important heterocycles. [30][31][32][33] Recently, we reported a metal-free, simple, and practical synthetic approach for the synthesis of 5-amino-1H-pyrrole-2-carboxylates via the iodine-catalyzed [3 + 2] cycloaddition reaction of substituted 2-benzylidene-malononitrile and ethyl glycinate hydrochloride. 34 However, to the best of our knowledge, the cyclization reaction utilizing ethyl glycinate hydrochloride has not been reported to construct furancarboxylates.…”