Abstract
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The reactivity of 3‐nitro‐4‐pyridyl isocyanate (7) and 5‐nitropyridin‐2‐yl isocyanate (9) in 1,3‐dipolar cycloaddition reactions with azides and pyridine N‐oxides has been investigated. 1,3‐Dipolar cycloaddition to trimethylsilylazide (TMSA) afforded the respective tetrazolinones, 1‐(3‐nitropyridin‐4‐yl)‐1__H__‐tetrazol‐5(4__H__)one (8, 50 %) and 1‐(5‐nitropyridin‐2‐yl)‐1__H__‐tetrazol‐5(4__H__)one (11, 64 %). Respectively, 1,3‐dipolar cycloaddition of nitropyridyl isocyanates 7 and 9 to 3,5‐dimethylpyridine N‐oxide (14), 3‐methylpyridine N‐oxide (21) and pyridine N‐oxide (22) gave the substituted amines, 3,5‐dimethyl‐N‐(3‐nitropyridin‐4‐yl)pyridin‐2‐amine (17), 3,5‐dimethyl‐N‐(5‐nitropyridin‐2‐yl)pyridin‐2‐amine (20), N‐(5‐nitropyridin‐2‐yl)pyridin‐2‐amine (24), 5‐methyl‐N‐(5‐nitropyridin‐2‐yl)pyridin‐2‐amine (23) and 3‐methyl‐N‐(5‐nitropyridin‐2‐yl)pyridin‐2‐amine (25) in 65 ‐ 80 % yield, obtained by cycloaddition, rearrangement and decarboxylation. The results demonstrate that the nitropyridyl isocyanates (7,9) readily undergo 1,3‐dipolar cyloaddition reactions similar to phenyl isocyanates.