Front Cover Picture: Recent Advances in the Synthesis of C2‐Functionalized Pyridines and Quinolines Using N‐Oxide Chemistry (Adv. Synth. Catal. 1/2021)

Abstract

There is a famous sentence in Tao Te Ching: “The Tao produced one. One produced two. Two produced three. Three produced all things.” In this front cover picture, Tai Chi stands for Tao, and “N” and “O” in the two circles represent N‐oxides of this paper. Thunder and lightning stimulate Tai Chi to produce everything, which is represented by the five elements of metal, wood, water, fire, and earth. Therefore, this picture indicates that pyridine N‐oxides can produce numerous nitrogen‐containing heterocyclic compounds under the action of activating reagent. Details can be found in the Review by Dong Wang and co‐workers (D. Wang, L. Désaubry, G. Li, M. Huang, S. Zheng, Adv. Synth. Catal. 2021, 363, 2–39; DOI: 10.1002/adsc.202000910).

Ultrasound-assisted transition-metal-free catalysis: a sustainable route towards the synthesis of bioactive heterocycles

“…Their versatile pharmacological application [117][118][119] including antimalarial, antimicrobial, anticancer, antiprotozoal, anti-HIV, antitubercular, etc., and materials science applications [120][121][122][123] like photovoltaic cells, photographic plates, and OLEDs have sparked interest in the development of an efficient methodology for their successive construction and subsequent functionalization. [124][125][126] The Rajanna group has demonstrated the synergic combination of 2,4,6-trichloro-1,3,5-triazine (TCTA) with N,N-dimethylformamide (DMF) as an effective Vilsmeier-Haack (VH) reagent for the ultrasound-assisted cyclization of acetanilides to form the substituted quinolines in high yield within 35-95 minutes (Scheme 27). 127 This reaction condition was proven to be extremely successful in delivering eleven different compounds.…”

Visible‐Light‐Mediated C‐2 Functionalization and Deoxygenative Strategies in Heterocyclic N‐Oxides

“…[12] Recently, Wang and co-workers published an excellent review article on C-2 (sp 2 À H) functionalization of pyridine-and quinoline N-oxides, partially dealing with visible light-induced methodologies. [13] Despite a spectacular advancements in this area, to the best of our knowledge, there has been no review article on visible light-induced deoxygenation and CÀ H functionalization of heterocyclic N-oxides. The present review article deals with the visible light-assisted methodologies for deoxygenation and CÀ H functionalization of heterocyclic N-oxides.…”

Direct C(sp3)–H allylation of 2-alkylpyridines with Morita–Baylis–Hillman carbonates via a tandem nucleophilic substitution/aza-Cope rearrangement

“…Pyridines are among the most important heterocyclic structural moieties in many biologically active natural products, pharmaceuticals, and agrochemicals [ 1 – 3 ]. Therefore, the development of efficient strategies for functionalized pyridine derivatives would be significant in many fields [ 4 – 7 ]. Although transition-mental-catalyzed allylic substitution reactions employing various nucleophilic or electrophilic allylic precursors have been extensively studied [ 8 – 10 ], limited strategies were reported for their application in the C(sp 3 )–H allylic functionalization of 2-alkylazaarenes.…”