Synthesis of quinoxaline derivatives through condensation of 1,2‐diaminobenzenes with β‐keto sulfoxides

The reaction of o ‐phenylenediamine with α‐methylsulfinylcyclohexanone and α‐methylsulfinylcyclopentanone in the presence of acetic acid afforded 1,2,3,4‐tetrahydrophenazine and 2,3‐dihydro‐1 H ‐cyclopenta[ b ]‐quinoxaline, respectively. 3,4‐Diaminotoluene and 3,4‐diaminochlorobenzene were reacted with α‐methyl‐sulfinylacetophenone to give a mixture of the corresponding 6‐ and 7‐substituted 2‐phenylquinoxaline. Condensation of 3,4‐diaminomethoxybenzene with α‐methylsulfinylacetophenone gave 7‐methoxy‐2‐phenylacetophenone, whereas, the same reaction between 3,4‐diaminonitrobenzene and α‐methylsulfinylacetophenone yielded 6‐nitro‐2‐phenylquinoxaline.