Comparative analysis of complanadine A total syntheses

• Reem Al-Ahmad and
• Mingji Dai

Beilstein J. Org. Chem. 2025, 21, 2334–2344, doi:10.3762/bjoc.21.178

• underwent ketone release and amine-ketone condensation to form iminium ion 27. Under the same acidic conditions, enamide 26 underwent hydrolysis and tautomerization to form enol 28. Conjugate addition of enol 28 to iminium ion 27 gave 29 for the subsequent intramolecular Mannich cyclization to deliver 30

Pathway economy in cyclization of 1,n-enynes

• Hezhen Han,
• Wenjie Mao,
• Bin Lin,
• Maosheng Cheng,
• Lu Yang and
• Yongxiang Liu

Beilstein J. Org. Chem. 2025, 21, 2260–2282, doi:10.3762/bjoc.21.173

• delivered tricyclic indole derivative 59 featuring an exocyclic Z-alkene (Scheme 13, path a). When the terminal substituent of the alkyne was an aryl group, C3-selective cyclization was triggered under BiCl3 catalysis to generate tricyclic iminium 60. Subsequent aryl-assisted Mannich cyclization efficiently

• activated ynamide. This sequence resulted in the formation of spiroindoleninium intermediate 130 (Scheme 27, path a). Subsequent intramolecular Mannich cyclization proceeded, yielding the 1H-pyrrolo[2,3-d]carbazole derivatives 131. When silica gel was utilized as the catalytic medium, the same Michael

Cu(OTf)₂-catalyzed multicomponent reactions

• Sara Colombo,
• Camilla Loro,
• Egle M. Beccalli,
• Gianluigi Broggini and
• Marta Papis

Beilstein J. Org. Chem. 2025, 21, 122–145, doi:10.3762/bjoc.21.7

• , hydrazines and alkenes with Cu(OTf)2 (20 mol %) in CH2Cl2 at reflux is a useful tool to access substituted 4,5-dihydropyrazoles 31 (Scheme 23) [40]. The products reasonably result from a Mannich/cyclization/oxidative transformation of the substrates in which Cu(OTf)2 is involved in more steps. The reaction

Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

Selective construction of dispiro[indoline-3,2'-quinoline-3',3''-indoline] and dispiro[indoline-3,2'-pyrrole-3',3''-indoline] via three-component reaction

• Ziying Xiao,
• Fengshun Xu,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2023, 19, 1234–1242, doi:10.3762/bjoc.19.91

• multicomponent reactions have been successfully developed to construct multifunctionalized or polycyclic spirooxindoles. For example, Zhang successfully developed a recyclable bifunctional cinchona/thiourea-catalyzed four-component Michael/Mannich cyclization sequence for the asymmetric synthesis of

Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

• (ee up to 92%). In the same year, Lautens and co-workers introduced a novel methodology for preparing enantioenriched N-heterocycles utilizing a Cu-catalyzed tandem conjugate borylation/Mannich cyclization sequence (Scheme 40A) [81]. The procedure was found to be generally relevant as several

Recent progress in the synthesis of homotropane alkaloids adaline, euphococcinine and N-methyleuphococcinine

• Dimas J. P. Lima,
• Antonio E. G. Santana,
• Michael A. Birkett and
• Ricardo S. Porto

Beilstein J. Org. Chem. 2021, 17, 28–41, doi:10.3762/bjoc.17.4

• amide, confirming to be a sample with a high level of enantiomeric purity. As in Murahashi’s synthesis, Meyers also utilized a chiral auxiliary for asymmetric induction. Nonetheless, this method differed from Murahashi's by presenting a diastereoselective intramolecular Mannich cyclization to form the

• prepared the (−)-adaline (1) and the non-natural isomer (−)-euphococcinine (2) through a four-step intramolecular Mannich cyclization cascade reaction [57]. In this methodology, the alkaloids were prepared by treating the convenient N-sulfinylamino ketone ketal precursor on heating with NH4OAc:HOAc. Oxo

• bromide provided ketones (+)-99 and (+)-100, in diastereoisomeric excess of about 92%. N-sulfinyl-β-aminoketone ketal (+)-99 was subjected to Mannich cyclization, via treatment with 25 equivalents of ammonium acetate in acetic acid at 75 °C, generating (−)-euphococcinine (2) in 90% yield. A similar

A novel and practical asymmetric synthesis of eptazocine hydrobromide

• Ruipeng Li,
• Zhenren Liu,
• Liang Chen,
• Jing Pan,
• Kuaile Lin and
• Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 2340–2347, doi:10.3762/bjoc.14.209

• were optimized to obtain the product in excellent overall yield and purity. Keywords: alkylation; asymmetric catalysis; eptazocine; Mannich cyclization; Introduction Eptazocine hydrobromide (1, Scheme 1), (1S,6S)-1,4-dimethyl-2,3,4,5,6,7-hexahydro-1H-1,6-methanobenzo[e]azonine-10-ol hydrobromide

• ) using the conditions in entry 9 and a similar yield was obtained (Table 2, entry 11). When cyano compound 12 was reduced by hydrogenation in the presence of Raney-Ni as catalyst in NH3/CH3OH, the proposed primary amine 13 was obtained in 73% yield. Then, for the Mannich cyclization, when 13 was reacted