4-Amino-3,5-dinitro-1,8-naphthyridine

Amino-dehydrogenation (SnH) using the LA/PP system was also studied with the 3,6-dinitro-l,8-naphthyridines (87a-87d) (86JHC473 93LA471). Besides mono amino products, diamino products are also obtained the yields are, however, moderate. 

The compounds 87a and 87b are aminated at position 4, yielding the 4-amino compound (88a, 40%) and the 2,4-diamino compound (88b, 11%) respectively the 2-ethoxy compound (87c), however, undergoes amination at position 4 as well at position 5, giving a mixture of the 4-amino compound (88c, 20%) and the 5-amino compound (89a, 14%).Tlie 2-chloro compound (87d) yields a highly complex reaction mixture from which the 5-amino compound (89b), the 2,4-diamino derivative (88b), and 2,5-diamino-l,8-naphthyridine (89c) could be isolated. l-Ethyl-3-nitro-l,8-naphthyridin-2(lH)-one (90a) and 3,6-dinitro-l-ethyl-l,8-naphthyridin-2(lH)-one (90b) were aminated exclusively in the 4-position to give compounds 91a (62%) and 91b (45%), respectively (93LA471). 

Taking into account the high reactivity of the ehloro atoms in 2-ehloro-3-nitro- (99a, 99d, and 99f), 7-ehloro-3-nitro- (99e and 99g), 2,7-diehloro-3-nitro- (99c), and 2-ehloro-3,6-dinitro-l,8-naphthyridines (99b), a great variety of 2- (or 7-) substituted amino produets [99, = NHCH3, N(CH3)Ph,... 

Oxidative amination of the easily accessible 2-R-3,5-dinitro-l,8-naphthyridines only takes place at C-4. With R = H, 4-amino-3,5-dinitro-... 

A solution of 2-chloro- and 2-amino-3,5-dinitro-l,8-naphthyridine in liquid ammonia shows the presence of a covalent adduct at C-4, as proved by NMR spectroscopy (83RTC359, 83RTC511, 83JHC9, 85JHC761, 93LAC 471, 00AHC(77)285). The NMR spectrum of a solution of 2-ethoxy-3,5-dinitro-l,8-naphthyridine and 2-chloro-3,5-dinitro-l,8-naphthyridine in liquid ammonia features the presence of two covalent adducts one at C-4 as well as one at C-5. The C-4/C-5 adduct ratio is found to be temperature dependent. For the 2-chloro compound the adduct ratio C-4/C-5 is 60/40 at —45°C, but changes to 40/60 at room temperature. This temperature dependency for the 2-ethoxy compound is more pronounced the C-4/C-5 adduct ratio is 50/50 at —45°C and 85/15 at room temperature. 

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