2020
DOI: 10.3390/molecules25092194
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Synthesis and Facile Dearomatization of Highly Electrophilic Nitroisoxazolo[4,3-b]pyridines

Abstract: A number of novel 6-R-isoxazolo[4,3-b]pyridines were synthesized and their reactions with neutral C-nucleophiles (1,3-dicarbonyl compounds, π-excessive (het)arenes, dienes) were studied. The reaction rate was found to be dependent on the nature of the substituent 6-R. The most reactive 6-nitroisoxazolo[4,3-b]pyridines are able to add C-nucleophiles in the absence of a base under mild conditions. In addition, these compounds readily undergo [4+2]-cycloaddition reactions on aromatic bonds C=C(NO2) of the pyridin… Show more

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Cited by 10 publications
(3 citation statements)
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References 47 publications
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“…The addition of an electron-donating group (−OCH 3 ) to the pronucleophile produced no significant change in ketene N , O -acetal production (Table , 23a–23c ), while the addition of an electron-withdrawing group (−NO 2 ) to the same molecule provided no desired product (eq ). Rather, induced electron deficiency (per nitro group in position 6) of the indole nucleus activated nucleophilic aromatic substitution of n -BuLi to the heterocycle (at position 7); , under these conditions, the peroxide underwent base-promoted Kornblum–DeLaMare fragmentation, as opposed to alkoxy transfer …”
Section: Resultsmentioning
confidence: 99%
See 1 more Smart Citation
“…The addition of an electron-donating group (−OCH 3 ) to the pronucleophile produced no significant change in ketene N , O -acetal production (Table , 23a–23c ), while the addition of an electron-withdrawing group (−NO 2 ) to the same molecule provided no desired product (eq ). Rather, induced electron deficiency (per nitro group in position 6) of the indole nucleus activated nucleophilic aromatic substitution of n -BuLi to the heterocycle (at position 7); , under these conditions, the peroxide underwent base-promoted Kornblum–DeLaMare fragmentation, as opposed to alkoxy transfer …”
Section: Resultsmentioning
confidence: 99%
“…and 2-(decylperoxy)­tetrahydro-2 H -pyran ( 13a , 1.00 equiv, 129.2 mg, 500. μmol) to provide no ketene N , O -acetal but, rather, 7-butyl-6-nitro-1-methylindole as a dark-brown oil, following isolation (35.9 mg, 31%). This product, formed by undesired nucleophilic aromatic substitution of n -BuLi, matched the predictions laid forth by previous groups . Characterization: R f = 0.32 (5% EtOAc/Hex); 1 H NMR (600 MHz, CDCl 3 ): δ 7.57 (d, J = 8.69 Hz, 1H), 7.48 (d, J = 8.69 Hz, 1H), 7.19 (d, J = 3.02 Hz, 1H), 6.53 (d, J = 3.02 Hz, 1H), 4.11 (s, 3H), 3.23 (t, J = 8.30 Hz, 2H), 1.85–1.77 (tt, J = 7.54, 7.54 Hz, 2H), 1.59–1.51 (tq, J = 7.54, 7.55 Hz, 2H), 1.02 (t, J = 7.55 Hz, 3H); 13 C­{ 1 H} NMR (150 MHz, CDCl 3 ): δ 145.6, 135.8, 133.8, 133.0, 123.1, 118.9, 116.6, 101.8, 37.5, 34.6, 26.9, 22.9, 13.9.…”
Section: Methodsmentioning
confidence: 99%
“…However, 2-chloropyridines are significantly more accessible than other 2-halopyridines because commercially available 2-hydroxypyridines can be easily chlorinated with various reagents like SOCl2, POCl3 or PCl5, especially after introduction of nitro group into position 3 or 5. Previously we have successfully applied Sonogashira coupling to 2-chloro-3-nitropyridines [4], but attempted Heck coupling gave no desired product due to side reactions of activated 2-chloropyridines at elevated temperatures.…”
Section: Synthesis Of 2-styryl-3-nitropyridinesmentioning
confidence: 99%