Functionalization of 4-bromobenzo[c][2,7]naphthyridine via regioselective direct ring metalation. A novel approach to analogues of pyridoacridine alkaloids

Recent Advances in Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds

This review surveys recent progress in the chemistry of polycyclic heteroaromatic molecules with a focus on structural diversity and synthetic methodology. The article covers literature published during the period of 2016-2020, providing an update to our first review of this topic (Chem. Rev. 2017, 117 (4), 3479-3716).

Oxidative Cyclization of Kynuramine and Ynones Enabling Collective Syntheses of Pyridoacridine Alkaloids

A cerium(III)-catalyzed oxidative cyclization of kynuramine and ynones has been reported as a key reaction in the total synthesis of marine pentacyclic pyridoacridine alkaloids featuring different ring connectivity patterns. The formation of tricyclic benzonaphthyridine rings was identified in the oxidative process. By combining with an intramolecular acylation and the chemoselective late-stage functionalization of pyridine rings, different approaches with 4-10 steps have been designed to accomplish the synthesis of alkaloids demethyldeoxyamphimedine (1), amphimedine (2), meridine (3), isocystodamine (4), N-methylisocystodamine (5), N-hydroxymethylisocystodamine (6), 9-hydroxyisoacididemin (7), neolabuanine A (8), and ecionine A (9).

Efficient Arylation of 2,7-Naphthyridin-1(2H)-one with Diaryliodonium Salts and Discovery of a New Selective MET/AXL Kinase Inhibitor

New 8-chloro-2-phenyl-2,7-naphthyridin-1(2H)-one building blocks bearing diverse substitutes on the 2-phenyl group were synthesized via an efficient diaryliodonium salt-based N-arylation strategy with the advantage of mild conditions, short reaction times, and high yields. A small combinatorial library of 8-amino substituted 2-phenyl-2,7-naphthyridin-1(2H)-one was further conveniently constructed based on the above chlorinated naphthyridinones and substituted aniline. Preliminary biochemical screening resulted in the discovery of the new 2,7-naphthyridone-based MET/AXL kinase inhibitors. More importantly, 17c (IC_50,MET of 13.8 nM) or 17e (IC_50,AXl of 17.2 nM) and 17i (IC_50,AXl of 31.8 nM) can efficient selectively inhibit MET or AXL kinase, respectively, while commercial cabozantinib showed no selectivity. The further exploration of the 8-substituted 2-phenyl-2,7-naphthyridin-1(2H)-one combinatorial library would significantly accelerate the discovery of more potent and selective inhibitors against diverse kinases.

A Predictive Model Towards Site-Selective Metalations of Functionalized Heterocycles, Arenes, Olefins, and Alkanes using TMPZnCl⋅LiCl

The development of a predictive model towards site-selective deprotometalation reactions using TMPZnCl⋅LiCl is reported (TMP=2,2,6,6-tetramethylpiperidinyl). The pKa values of functionalized N-, S-, and O-heterocycles, arenes, alkenes, or alkanes were calculated and compared to the experimental deprotonation sites. Large overlap (>80 %) between the calculated and empirical deprotonation sites was observed, showing that thermodynamic factors strongly govern the metalation regioselectivity. In the case of olefins, calculated frozen state energies of the deprotonated substrates allowed a more accurate prediction. Additionally, various new N-heterocycles were analyzed and the metalation regioselectivities rationalized using the predictive model.