The reaction of the ninhydrin (1) with 1,2‐bishydroxylamines 2a–c affords dihydroindeno[1,2‐b]pyrazine N,N′‐dioxides 5a–c. The intermediates hexahydro‐ and tetrahydroindeno[1,2‐b]pyrazines 3a and 4c, which have been isolated, are easily transformed into 5a, c. Heating of 5b, c or keeping of 5b on alumina gives indeno[1,2‐b]pyrazine N‐oxides 6b, c, N,N′‐dioxide 7c and indeno[1,2‐b]pyrazine 8. Treatment of 5b with a solution of hydrochloric acid in H2O/MeOH leads to 6b, whereas treatment of 5b with KOH furnishes mono‐N‐oxides 6b, 9 and dioxide 7b. Compound 8 is prepared by deoxygenation of 6b with TiCl3. The reduction of 6b with NaBH4 yields alcohol 10 and the reaction of 6b with NH2OH/AcOH gives a mixture of isomeric oximes (E)‐11 and (Z)‐11. Copyright © 1994 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim