The nitroalkene showing dual behaviors in the same reaction system

Recent Progress in Nitro-Promoted Direct Functionalization of Pyridones and Quinolones

“…This is the first example of a nitroalkene that exhibits dual behavior in the same reaction mixture ( Figure 5). Interestingly, a quinolino [3 ,4-b] [1,9]diazaphenanthrene derivative 22 is formed when the same reaction is conducted in the presence of triethylamine (Scheme 5) [38]. A plausible mechanism is shown in Scheme 6.…”

“…Indeed, the cycloaddition of 16 with cyclopentadiene proceeds smoothly to furnish a tetracyclic compound 17 that aromatizes via elimination of a nitrous acid in the presence of triethylamine to afford compound 18 [37]. Similarly, the cycloaddition using α,β-unsaturated oxime, instead of cyclopentadiene, as a heterodiene affords the polycyclic diazaphenanthrene 19 (Scheme 4) [38]. On the contrary, 1-methyl-3,6,8-trinitro-2-quinolone 16 undergoes cycloaddition with dienes easily under mild conditions (Scheme 3).…”

“…On the other hand, it serves as a heterodiene in reaction with an electron-rich alkene to construct an oxazine ring. The nitroalkene moiety of trinitroquinolone 16 also serves as a heterodiene in the reaction with ethoxyethene to construct a fused oxazine ring 20 (Scheme 5) [38], which yields an acetal 21 via ring-opening reaction upon treatment with alcohol under reflux conditions. Interestingly, a quinolino[3 ,4-b] [1,9]diazaphenanthrene derivative 22 is formed when the same reaction is conducted in the presence of triethylamine (Scheme 5) [38].…”

Chemistry of Nitroquinolones and Synthetic Application to Unnatural 1-Methyl-2-quinolone Derivatives

“…The cycloadduct is easily converted to an acetal by the ring opening reaction upon heating in alcohol. On the other hand, a quinolino[3,4- b ][1,9]diazaphenanthrene derivative is formed when the same substrates are treated in the presence of triethylamine ( Scheme 19 ) [ 51 ].…”

“…The cycloaddition of intermediate A with another molecule of TNQ constructs a new pyridine ring, and the subsequent aromatization furnishes the polycyclic product together with elimination of nitrous acid and water. In the present process, the former oxime A behaves as an electron-rich heterodiene and the latter TNQ behaves as an electron-poor dienophile [ 51 ]. This mechanism is supported by the experimental fact that polycyclic diazaphenanthrene is isolated in a moderate yield as a result of cycloaddition of TNQ with α,β-unsaturated oxime as the electron-rich heterodiene ( Scheme 20 ).…”