Quinoxalines. XIII. : On the Reaction of 2-(Methylsulfonyl)-quinoxaline with Ketones. (2)

Reaction of 2-(methylsulfonyl) quinoxaline (I) and ketone (II) was carried out in benzene, in the presence of sodium amide. The ketones used were acetophenone (IIa), propiophenone (IIb), diethyl ketone (IIc), acetone (IId), methyl ethyl ketone (IIe), methyl propyl ketone (IIf), methyl isopropyl ketone (IIg), cyclopentanone (IIh), and cyclohexanone (IIi) (Chart 1). Only IIc did not undergo this reaction and others respectively afforded 2-(2-quinoxalinyl) acetophenone (IIIa), 2-(2-quinoxalinyl) propiophenone (IIIb), 1-(2-quinoxalinyl)-2-propanone (IIId), 1-(2-quinoxalinyl)-2-butanone (IIIe), 1-(2-quinoxalinyl)-2-pentanone (IIIf), 1-(2-quinoxalinyl)-3-methyl-2-butanone (IIIg), 2-(2-quinoxalinyl) cyclopentanone (IIIh), and 2-(2-quinoxalinyl) cyclohexanone (IIIi) (Chart 2 and Table I). It was assumed that, among these products, only IIIb would be difficult to effect enolization (Chart 4).