Quinoxalines. XIX. On the Reaction of 2-(Methylsulfonyl)quinoxaline with Ketone in Dimethyl Sulfoxide in the Presence of Potassium Cyanide

Reaction of 2-(methylsulfonyl)quinoxaline (I) and acetophenone (IIIa) in dimethyl sulfoxide, in the presence of potassium cyanide, at 100° results in the formation of 2-pheny1furo[2, 3-b]quinoxaline (VIa) accompanying 2-quinoxalinecarbonitrile (IV) and 2, 3-quinoxalinedicarbonitrile (V). In order to examine the process of formation of VIa, the same reaction was carried out with IV or V in place of I, and VIa was formed in either case, as well as by the application of potassium cyanide to 2-(2-quinoxalinyl)-acetophenone (VIIa). Therefore, formation of VIa cannot be concluded as a single process. The use of propiophenone (IIIb) as the ketone gave 3-methyl-2-phenylfuro-[2, 3-b] quinoxaline (VIb). The same reaction with ketones was carried out with 2-chloroquinoxaline (II) in place of I, and V was obtained in all cases. In addition, VIb was obtained from IIIb and 3-ethyl-2-phenylfuro[2, 3-b]quinoxaline (VIc) from butyrophenone (IIIc). In these reactions, yield of furo[2, 3-b]quinoxaline derivatives was extremely low, and it seems better to use the reaction of 2, 3-dichloroquinoaline (IX) with various ketones in benzene, in the presence of sodium amide, 3) to obtain such derivatives, but this reaction can also be carried out in dimethyl sulfoxide, in the presence of potassium cyanide ; for example, VIb is obtained from IX and IIIb.