V. M. Ostrovskaya, A. Tsygankov, S. Nefedov
Jun 1, 2006
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Journal
Russian Chemical Bulletin
Abstract
An improved procedure was proposed for the synthesis of 3-hydroxy-7,8-benzo-1,2,3,4-tetrahydroquinoline, which is used as a reagent for the analytical test reaction for nitrate and nitrite anions based on azo coupling with diazo compounds. 3-Hydroxy-6-(R-phenylazo)-7,8-benzo-1,2,3,4-tetrahydroquinolines (R = 2-COOH, 4-COOH, or 4-SO3H) were synthesized by azo coupling reactions in 65–70% yields. The structures of these compounds were confirmed by elemental analysis, 1H NMR and IR spectroscopy, and X-ray diffraction. Based on the X-ray data, the bathochromic shift in the UV spectrum of the o-carboxy isomer compared to the p-carboxy isomer (Δλmax = 50 nm) is attributed to a strong intramolecular hydrogen bond.