Polynuclear Compounds with More than One Nitrogen Ring

6 Polynuclear Compounds with More than One Nitrogen Ring 

The transformation to the 1,2,3,4-tetrahydro derivatives is best accomplished by hydrogenating the 2-alkyl-p-carboline salts in methanol adjusted to pH 10 with potassium hydroxide, as shown for alstonine hydrochloride (37) (eq. 12.65),124 or hydrogenating the anhydronium base in methanol, as shown with 2-methylharman (38) (eq. 12.66).125 

2 Phenanthrolines. Searles and Warren hydrogenated 4,7-phenanthroline (39) over Raney Ni in ethanol in the presence of sodium ethoxide and obtained a mixture of 5,6-dihydro and 1,2,3,4-tetrahydro derivatives (eq. 12.67).127 In the case of 2-methylphenanthroline, 2-methyl-7,8,9,10-tetrahydrophenanthroline was produced concurrently with 2-methyl-5,6-dihydrophenanthroline. 

When 4,7-phenanthroline was hydrogenated over platinum oxide in 1 1 AcOH-EtOH at near-atmospheric pressure, about 2 mol of hydrogen were taken up and the product was a mixture from which only 1,2,3,4-tetrahydrophenanthroline was isolated in nearly 40% yield.128 

Hydrogenation of 1,10-phenanthroline (40) with Raney Ni under conditions similar to those used for 39 afforded the 1,2,3,4-tetrahydro derivative in 80% yield (eq. 

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