Perhydropyrido pyridazine

The values of perhydropyrido[l,2-f)]pyridazine and its 2-oxo derivative were found to be 2.80 0.04 and 7.32 0.03, respectively (72KGS220), whereas that of anhydro 4-hydroxy-2-methyl-5,6,7,8-tetrahydropyrido(l,2-6]pyridazinium hydroxide (16) was determined by spectrophotometry to be 2.77 (71CPB159). UV spectroscopic measurements in sulfuric acid gave a pKa value of -0.25 for pyrido[l,2-6]cinnoline derivative (17, R = H) (74JHC125). 

When the hydrochloride salt of 2,3,4,4a,5,6-hexahydro-l//-pyridazino [1,6-a]quinoline was subjected to catalytic hydrogenation in ethanol over Pt02, 3-[2-(l,2,3,4-tetrahydroquinolyl)]propylamine was obtained (66YZ608). Catalytic reduction of perhydropyrido[l,2-ft]pyridazine over a skeletal nickel catalyst in ethanol at 30 atm gave ring-opened 2-(3-aminopropyl)piperidine (66KGS91). 

Perhydropyrido[l,2-6]pyridazine was prepared from perhydropyrido [l,2-fc]pyridazin-2-one by reduction with LAH (65MI1, 65URP170506 66KGS91 78JA4012), and from 4,4a,5,6,7,8-hexahydro-3//-pyrido[l,2-b] pyridazine by catalytic reduction over Pt02 in acetic acid (68YZ216). Re-... 

The cyano group of l-(cyanomethyl)perhydropyrido[l,2-h]pyridazine was reduced with LAH to yield the l-(2-aminoethyl) derivative (66KGS91). The amino group was reacted with methyl isothiourea in boiling 50% aqueous ethanol to afford the l-(2-guanidinoethyl) derivative (66KGS91). 

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