The unique reactivity of 5,6-unsubstituted 1,4-dihydropyridine in the Huisgen 1,4-diploar cycloaddition and formal [2 + 2] cycloaddition

• Xiu-Yu Chen,
• Hui Zheng,
• Ying Han,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2023, 19, 982–990, doi:10.3762/bjoc.19.73

• ; isoquinolino[1,2-f][1,6]naphthyridine; Introduction Among various well-known cycloaddition reactions such as the 1,3-dipolar cycloaddition reaction, Diels–Alder reaction, and the Povarov reaction, the cycloaddition reaction of Huisgen 1,4-dipoles with activated alkenes received increasing attention [1][2][3

• -fused tetrahydroquinolines (reaction 1 in Scheme 1) [41][42]. Menéndez and co-workers reported a Yb(OTf)3-mediated Povarov reaction of imines and N-alkyl-1,4-dihydropyridines for the synthesis of hexahydrobenzo[h][1,6]naphthyridines (reaction 2 in Scheme 1) [43]. Khan and co-workers employed a one-pot

• Povarov reaction of 3-aminocoumarins, aldehydes, and 5,6-unsubstituted 1,4-dihydropyridine derivatives for the construction of exo-hexahydrochromeno[3,4-h][1,6]naphthyridine-3-carboxylate derivatives (reaction 3 in Scheme 1) [44]. In these reactions, the 5,6-unsubstituted 1,4-dihydropyridines usually

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• tautomer 147, and the CPA-catalysed Povarov reaction between them gives the enantioenriched THQ 144 in good yields and enantioselectivities (4 examples, up to 97:3 er). This reactivity has been extended to enamides 148, with the imine generated from the α-amino acid 149 now reacting with 148 in a CPA

• -catalysed Povarov reaction rather than with its own tautomer (Scheme 21a) [70]. Zhang and You developed a catalytic dearomatisation reaction of indoles 150 using similar chemistry, where the generated imine 151 now reacts intramolecularly with a pendant nucleophile and is further oxidised to a carbocation

Selectivity in multiple multicomponent reactions: types and synthetic applications

• Ouldouz Ghashghaei,
• Francesca Seghetti and
• Rodolfo Lavilla

Beilstein J. Org. Chem. 2019, 15, 521–534, doi:10.3762/bjoc.15.46

• the Union Concept. A) Petasis-Ugi combination; B) GBB-Ugi/Passerini combination; C) Reissert MCRs linked to a Povarov reaction. Selective MMCRs featuring FGs with distinct reactivity along the sequence. A) Synthesis of aminomethyltetrazoles by consecutive isocyanide MCRs. B) Interrupted Ugi/Joullié

Aza-Diels–Alder reaction between N-aryl-1-oxo-1H-isoindolium ions and tert-enamides: Steric effects on reaction outcome

• Amitabh Jha,
• Ting-Yi Chou,
• Zainab ALJaroudi,
• Bobby D. Ellis and
• T. Stanley Cameron

Beilstein J. Org. Chem. 2014, 10, 848–857, doi:10.3762/bjoc.10.81

• major highlight of this work. Results and Discussion Our literature search revealed that although tert-enamides have been used as dienophiles for the Povarov reaction to build 1,2,3,4-tetrahydroquinoline blocks [25][26][37], there were no reports of their usage in the inverse electron demand hetero

Facile synthesis of functionalized tetrahydroquinolines via domino Povarov reactions of arylamines, methyl propiolate and aromatic aldehydes

• Jing Sun,
• Hong Gao,
• Qun Wu and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2012, 8, 1839–1843, doi:10.3762/bjoc.8.211

• proceeded smoothly to give polysubstituted 1,2,3,4-tetrahydroquinolines in moderate yields. The reaction is believed to involve the Povarov reaction of in situ generated β-enamino ester with the in situ formed aromatic imine. Keywords: β-enamino ester; domino reaction; electron-deficient alkyne; Povarov

• developed as the most powerful synthetic routes to construct oxygen or nitrogen-containing six-membered heterocycles [4][5][6][7][8]. In recent years, the imine Diels–Alder reaction (also known as Povarov reaction) and the [4 + 2] cycloaddition reaction of imines (obtained from the corresponding aromatic

• ]. However, a survey of literature reveals that a Povarov reaction with in situ generated β-enamino ester as dienophile has not been reported until now. Recently, Zhu and Masson successfully developed three-component Povarov reactions using enamides as dienophiles leading to a highly efficient synthesis of