3-Iodo-4- cinnoline

Nitration of pyrido[l,2-f>]cinnolin-6-ium hydroxide inner salt 17 (R = H) and its 2-acetamide derivative afforded its 2-nitro and 2-acetamido-3-nitro derivatives, respectively. The reaction of 17 (R = H) with iodine monochloride afforded the 2-iodo derivative. The 2-cyano derivative was obtained from the 2-bromo derivative of 17 (R = H) with Cu(I)CN. Treatment of 17 (R = H) with P4S10 afforded the 11-mercapto derivative 41 (74JHC125). 

Coupling of terminal acetylenes with 3-chloropyridazines has been performed, using the Pd -Cu -EtjNH system, giving 3-(alkynyl)pyridazines in yields of up to 78% phenylacetylene gives (90) with 3-chloropyridazine 1-oxide but only gives tars with the isomeric 2-oxide/ 3-(Alkynyl)cinnolines have been similarly prepared from 3-iodo- and 3-bromo-cinnolines, and attempts to couple alkenes have been reported it is not unusual, in this type of reaction, to obtain small amounts of homo-coupling products i.e. biaryls), but an excellent yield of 3,3 -bicinnolinyl (81%) was obtained from 3-bromo-cinnoline and styrene. 

Halogeno substituents at the 3- or 4-position of cinnoline are appreciably activated by N2 and Nl, respectively those at positions 5-8 or an extranuclear position have activities only marginally better than those in corresponding carbo-cyclic compounds. There seems to be little difference in reactivity of a fluoro, chloro, bromo, or iodo substituent at the same position. 

Iodo-4(17/)-cinnolinone (73) with phenylacetylene in the presence of appropriate catalysts gave 2-phenylfuro[3,2-c]cinnoline (74) [(Ph3P)2PdCl2, Cul, OP(NMe2)3, EtaN, N2, 20°C, 6h 49%] analogs likewise. ... 

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