Alkaline condensation of 9,10-phenanthrenedione with N,N-dialkylguanidines. A novel synthesis of 2′-(dialkylamino)spiro[9H-fluorene-9,4′-[4H]imidazol]-5′(3′H)ones

9,10-Phenanthrenedione was reacted with equimolar amounts of N,N-dimethylguanidine or creatine in 0.2 N potassium hydroxide in ethanol-water, 7:3 to obtain 2′-(dimethylamino)spiro-9H-fluorene-9,4′-4H]imidazol]-5′(3′H)one or N-(3′,5′-dihydro-5′-oxospiro9H-fluorene-9,4′-4H]imidazol]-2′-yl)-N-methylglycine, respectively. These products are the first derivatives of this ring system with 2′-amino substituents. Formation of these products accounts for the previously reported absence of fluorescence when 9,10-phenanthrenedione reacts with N,N-di-substituted guanidines.