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Site-Selective C-H Alkylation of Diazine <i>N</i>-Oxides Enabled by Phosphonium Ylides
Ghosh, Prithwish,Kwon, Na Yeon,Han, Sangil,Kim, Saegun,Han, Sang Hoon,Mishra, Neeraj Kumar,Jung, Young Hoon,Chung, Sang J.,Kim, In Su American Chemical Society 2019 ORGANIC LETTERS Vol.21 No.16
<P>The synthesis of alkylated diazine derivatives is important for their practical utilization as pharmaceuticals and for other purposes. Herein, we describe the metal-free site-selective C-H alkylation of diazine <I>N</I>-oxides using phosphonium ylides that affords a variety of alkylated diazine derivatives with broad functional group tolerance. The utility of this method is showcased by the late-stage functionalization of a commercially available drug such as varenicline. Notably, the sequential C-H alkylation of pyrazine <I>N</I>-oxides for the total synthesis of a pyrazine-containing natural product, paenibacillin A, highlights the importance of this method.</P> [FIG OMISSION]</BR>
Jin Ho Choi,Hak Do Kim,강주영,정태주,ghosh prithwish,In Su Kim 대한화학회 2021 Bulletin of the Korean Chemical Society Vol.42 No.3
The ruthenium(II)-catalyzed C?H carbonylation of 2-aryl quinazolinones with isocyanates as carbonyl sources is described. The developed method provides direct access to biologically relevant isoindoloquinazolinone core through C?H aminocarbonylation followed by intramolecular annulation. A broad range of substrate scope and functional group tolerance were observed. Gram-scale reactions and synthetic transformations demonstrate the synthetic potential of this protocol.
Site-selective and metal-free C–H nitration of biologically relevant N-heterocycles
Junghyea Moon,Hyun Ku Ji,Nayoung Ko,Harin Oh,Min Seo Park,Suho Kim,Prithwish Ghosh,Neeraj Kumar Mishra,김인수 대한약학회 2021 Archives of Pharmacal Research Vol.44 No.11
The site-selective and metal-free C–H nitrationreaction of quinoxalinones and pyrazinones as biologicallyimportant N -heterocycles with t -butyl nitrite is described. Awide range of quinoxalinones were effi ciently applied in thistransformation, providing C7-nitrated quinoxalinones withoutundergoing C3-nitration. From the view of mechanisticpoint, the radical addition reaction exclusively occurred atthe electron-rich aromatic region beyond electron-defi cientN -heterocycle ring. This is a fi rst report on the C7–H functionalizationof quinoxalinones under metal-free conditions. In contrast, the nitration reaction readily takes placeat the C3-position of pyrazinones. This transformation ischaracterized by the scale-up compatibility, mild reactionconditions, and excellent functional group tolerance. Theapplicability of the developed method is showcased by theselective reduction of NO 2 functionality on the C7-nitratedquinoxalinone product, providing aniline derivatives. Combinedmechanistic investigations aided the elucidation of aplausible reaction mechanism.