Some quinoline-5 : 8-quinones

Synthesis of 1-azabenzo[a]phenoxazin-5-one and 11-amino-1,8,10-triazabenzo[a]phenoxazin-5-one and their functionalized aryl derivatives via Mizoroki-Heck arylation methodology

“…The residue was recrystallized from ethanol to afford a bright yellow crystal of 8-hydroxy-5-nitroquinoline. Yield 14.10 g (90.1%), mp 179 °C (lit 179.5-181.5°C ) 20 .…”

“…The mixture was then filtered and washed with water and the residue recrystallized from aqueous ethyl acetate to afford 7-chloro-8-hydroxy-5-nitroquinoline as a bright orange solid. Yield 8.50 g, (88%), mp 233-234 °C (lit 235 °C) 20 . The presence of the chloro group was confirmed using sodium fusion 21 .…”

“…The chlorination of 8-hydroxy-5-nitroquinoline (11) was achieved using the literature 20 . 8-Hydroxy-5-nitroquinoline (11) (10 g) was suspended in water (1 L) in a two liter beaker and potassium hydroxide (1 M, 45 mL) was added.…”

“…The oxidation of 8-hydroxy-5-nitrosoquinoline (10) to 8-hydroxy-5-nitroquinoline (11) was carried out according to the procedure of Petrow and Sturgeon 20 . Finely grounded 8-hydroxy-5-nitrosoquinoline hydrochloride (10) (15.0 g, 0.7 mmol) was added into a 500 mL beaker containing concentrated nitric acid (45 mL) and water (30 mL) in an ice bath.…”

Regioselective Bromination of 5,8-Dimethoxyquinoline with N-Bromosuccinimide

“…Previously, for example, both 6-bromoquinoline-5,8-dione and 7-bromo analog were directly prepared in low yields (0-15% and 5-18% respectively) from a one-step oxidative bromination 6 (NBS/AcOH-H 2 O) of 8-hydroxyquinoline. So far, the only practical method that leads to 7-bromoquinoline-5,8-dione is a three-step route 7,8 consisting of (i) regioselective bromination (NBS/THFcat.H 2 SO 4 ) of 5-nitro-8-hydroxyquinoline at C(7) position, (ii) reduction of the nitro group using Na 2 S 2 O 4 to the corresponding amine, and (iii) oxidative pquinone formation under rather harsh conditions (K 2 Cr 2 O 7 -H 2 SO 4 ). Seeking a new and milder route to 7-bromoquinoline-5,8-dione, we selected on the use of 5,8-dimethoxyquinoline 1, a readily available material by the condensation of 2,5-dimethoxyaniline with acrolein.…”