Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• mechanism of the formation of phenolic Mannich bases is similar to that discussed above for the synthesis of amidoalkylnaphthols. First, the phenol component reacts with the aldehyde to form the o-QM intermediate, which reacts in a nucleophilic addition step with the amine component, resulting in

• . This results in differences in both the formation and stability of o-QM. Grimaud et al. synthesized Mannich bases starting from N-benzylpiperazine, various aldehydes and substituted phenols [63]. The intermediate Mannich adducts 8a–i were then reacted with 5,5-dimethylcyclohexane-1,3-dione or 1-methyl

• ]. As reported in both papers, Mannich bases formed 9a–t were isolated in good yields. Plausible reaction pathways were described and the energetic values of the transition states were calculated. In one of the latest publications with respect to this topic, Priya et al. disclosed the synthesis of a

Aminomethylation/hydrogenolysis as an alternative to direct methylation of metalated isoquinolines – a novel total synthesis of the alkaloid 7-hydroxy-6-methoxy-1-methylisoquinoline

• Benedikt C. Melzer,
• Jan G. Felber and
• Franz Bracher

Beilstein J. Org. Chem. 2018, 14, 130–134, doi:10.3762/bjoc.14.8

• derivative 5 in reasonable yield. Later on, hydrogenolytic cleavage of the generated benzylamine-type group at C1 should give the desired 1-methyl moiety. Related reductive cleavage reactions have been published earlier by Möhrle [20] for phenolic Mannich bases in the course of the total synthesis of the

• phenolic product 6 in high yield with unchanged N,N-dimethylaminomethyl group. The same result was obtained at high pressure (40 bar) and upon addition of formic acid for accelerating hydrogenolysis [21]. Obviously, and in contrast to earlier reports on related naphthol Mannich bases [20], the benzylamine

The simple production of nonsymmetric quaterpyridines through Kröhnke pyridine synthesis

• Isabelle Sasaki,
• Jean-Claude Daran and
• Gérard Commenges

Beilstein J. Org. Chem. 2015, 11, 1781–1785, doi:10.3762/bjoc.11.193

• pyridine synthesis; Mannich bases; platinum; X-ray diffraction; Findings Polypyridines have been demonstrated to be useful building blocks in metallo-supramolecular chemistry [1][2][3]. In particular, polypyridines joined at the 2,6-position have the ability to accommodate different coordination numbers

Multicomponent reactions in nucleoside chemistry

• Mariola Koszytkowska-Stawińska and
• Włodzimierz Buchowicz

Beilstein J. Org. Chem. 2014, 10, 1706–1732, doi:10.3762/bjoc.10.179

• as Mannich bases) can serve as starting materials in the syntheses of a variety of compounds. The employment of a nucleoside as the hydrogen active component has been one of the most common variants of the Mannich reaction. Treatment of uracil (or 2-thiouracil) nucleosides 1 with aq formaldehyde and