63543-87-3Relevant academic research and scientific papers
Intramolecular hydrogen bonding in 8-quinolinol N-oxides, quinaldinic acid N-oxides and quinoline-2-carboxyamide N-oxide. Deuterium isotope effects on 13C chemical shifts
Dziembowska, Teresa,Rozwadowski, Zbigniew,Hansen, Poul Erik
, p. 189 - 199 (1997)
Secondary isotope effects on 13C chemical shifts have been measured in a series quinolinols, quinaldinic acid N-oxides and quinoline-2-carboxyamide N-oxide. For 8-quinolinol N-oxides a good correlation was found between δOH and (n)ΔC(OD) isotope effects. The OH and 13C chemical shifts and (n)AC(OD) show very small temperature dependences. The primary isotope effects are small, positive and temperature insensitive. Furthermore, they increase with increasing (n)AC(OD). All features point towards a localised hydrogen bond in an asymmetric double well potential. The quinaldinic acid N-oxides show long-range isotope effects on 13C chemical shifts of both signs with 2AC=O(OD) rather small. The primary isotope effects of the quinaldinic acid N-oxide is of order of 0.5 ppm, whereas for its 4-ethoxy-derivative is smaller, ~0.3 ppm. The OH chemical shifts resonate at the low field ~ 18-20 ppm and the OH resonance is fairly broad at room temperature, especially for the 4-ethoxy-derivative. The temperature effects on the chemical shifts, primary and secondary isotope effects are small. For quinaldinic acid N-oxides the asymmetric broad quasi-single potential is suggested. For quinoline-2-carboxyamide N-oxide the isotope effects are small, indicating rather weak hydrogen bond.
C2-Selective C-H methylation of heterocyclic N-oxides with sulfonium ylides
An, Won,Choi, Su Bin,Kim, Namhoon,Kwon, Na Yeon,Ghosh, Prithwish,Han, Sang Hoon,Mishra, Neeraj Kumar,Han, Sangil,Hong, Sungwoo,Kim, In Su
supporting information, p. 9004 - 9009 (2020/11/30)
A redox-neutral C2-selective methylation of heterocyclic N-oxides with sulfonium ylides is described herein. This report presents unprecedented findings for the utility of sulfonium ylides as the methylation source of N-heterocycles beyond the Corey-Chaykovsky reaction. Intriguingly, pyrrolidine plays a significant role in minimizing the reductive C2-methylation process. This method is characterized by its mild conditions, simplicity, and excellent site selectivity. The applicability of the developed protocol is showcased by the late-stage methylation and sequential transformations of complex drug molecules.
Transition-Metal-Free Regioselective Alkylation of Quinoline N-Oxides via Oxidative Alkyl Migration and C?C Bond Cleavage of tert-/sec-Alcohols
Sen, Chiranjit,Ghosh, Subhash C.
, p. 905 - 910 (2018/01/11)
An unprecedented C2-alkylation of quinoline N-oxide derivatives via C?C bond activation of tert- and sec-alkyl alcohol is described using hypervalent iodine (III) reagent PhI(OAc)2 (PIDA). This regioselective alkylation using mild hypervalent iodine reagents is more practical, operationally simple and transition metal free. The reaction proceeds efficiently with a broad range of substrates including quinoline, isoquinoline, and pyridine N-oxides using a variety of tert-/sec- alcohols. From experimental outcome, we also propose a rationalized mechanism, mediated by PIDA. (Figure presented.).
Benzylation of heterocyclic N-oxides via direct oxidative cross-dehydrogenative coupling with toluene derivatives
Wan,Qiao,Sun,Di,Fang,Li,Guo
supporting information, p. 10227 - 10232 (2016/12/07)
A novel cross-dehydrogenative coupling (CDC) of heterocyclic N-oxides with toluene derivatives has been discussed, allowing for the facile synthesis of a broad range of structurally diverse C1-benzyl quinoline N-oxides, isoquinoline N-oxides and pyridine N-oxides, including two methylated quinoline N-oxides in particular. This protocol not only extends the application of toluenes in synthetic organic chemistry, but also offers an alternative method to prepare benzylated heterocyclic N-oxides without any metal involved, which is important in medicinal chemistry.
