Bromine 4 equiv. 2 equiv. 2 equiv. 3 equiv. 4 equiv. 3 equiv. 6 equiv. 4 equiv. 2 equiv. 5 equiv. Time 3.5 h 30 rnin 40 min 30 min 30 rnin 30 min 10 min 15 min 1.5 h 2 h Yield (%) 75 51 46 86 46 46 50 46 97 64 Paper 9/01 877H

The 1,6‐disubstituted‐ and 4,6‐disubstituted‐11‐aza‐5H‐benzo[a]phenoxazin‐5‐one as well as 6‐substituted‐11‐aza‐5H‐pyrido[a]phenoxazin‐5‐one derivatives were prepared by the condensation of 2‐amino‐3‐hydroxypyridine with 5‐substituted‐2,3‐dihalogeno‐1,4‐naphthoquinones and 6,7‐dibromo‐5,8‐quinolinequinone respectively. The resulting compounds were subjected to reduction, acetylation, dehalogenation and reaction with aniline.

The regioselective addition of lithium enolates to thio-substituted 1,4-naphthoquinones gave alkylated 1,4-naphthoquinones via 1,4-addition products. A phenacyl 1,4-naphthoquinone was cyclized to a naphthofuran-4,9-dione ring system.

The acid‐catalysed reaction of substituted 1,4‐naphthoquinones with o‐aminoheterocyclic thiones in alcoholic solution afforded substituted monoazabenzo[a]phenothiazin‐5‐ones 4,5 and substituted benzo[a][1,4]diazabenzothiazino[3,2‐c]phenothiazin‐5‐one (6). Some of the resulting compounds were subjected to dehalogenation. The structures of the products were assigned by elemental analysis, 1H‐nmr, and other spectral analysis.

Acid-catalyzed reductive cyclization of 2-alkylsubstituted 3-ethylthio- and 3-phenylthio-1,4-naphthoquinones gave naphtho[1,2-b]furans in high yields.