811. Cinnolines. Part XXXV. Studies of the chloro- and hydroxy-cinnolines

Abstract

Osbom a+id Schojeld. 4207 811. Cinnolines. Part XXXV." Studies of the Chloroand Hydroxy-cinnolines.

Cyclization of 1-(2-Alkynylphenyl)-3,3-dialkyltriazenes: A Convenient, High-Yield Synthesis of Substituted Cinnolines and Isoindazoles

“…Interestingly, more than half of the 6-substituted cinnolines are new compounds despite their simple structures. Aside from the parent heterocycle, which is commercially available, our method permits much easier access to the known cinnolines ( 60 , 61 , 65 ) and in considerably higher overall yields. Compounds 63 and 64 reflect the versatility of this cyclization as their acid-sensitive functionalities would not survive the harsh conditions typical of previous cinnoline syntheses …”

“…6-Chlorocinnoline (61). Obtained from 29 using general procedure E (yellow solid, 97%): mp 128.8−129.9 °C (lit . mp 131−131.5 °C); 1 H NMR (CDCl 3 ) δ 9.30 (d, J = 6.2 Hz, 1H), 8.47 (dd, J = 9.1, 0.6 Hz, 1H), 7.82 (d, J = 2.1 Hz, 1H), 7.77 (d, J = 6.2 Hz, 1H), 7.76 (dd, J = 9.1, 2.1 Hz, 1H); 13 C NMR (CDCl 3 ) δ 149.16, 145.50, 137.45, 131.97, 131.66, 126.59, 125.21, 121.44; IR (KBr) 3061, 3034 cm -1 .…”

Methods for the synthesis of cinnolines (review)

“…While refuting the hypothesis about the initial hydration of the triple bond in the course of the Richter reaction, the authors put forward the alternative suggestion that the reaction begins with coordination of the diazonium cation to the triple bond followed by the addition of a water molecule [67]. Later on during study of the acidity constants and UV spectra of various hydroxycinnolines it was shown that 4-hydroxycinnolines exist in the form of the other tautomeric form -4-(1H)-cinnolinones [69,70].…”