The reaction of heteroaromatic N-oxide with acid chloride and cyanide. III. On the reaction of quinoline N-oxides with sulfonic acid chloride and potassium cyanide (author's transl)

Abstract

The reaction of quinoline 1-oxide (I) with both methanesulfonyl chloride (S) and potassium cyanide in a mixture of acetone-water gave 2-(methylsulfonyl) quinoline (II) containing a small proportion of 4-(methylsulfonyl) quinoline (III). As a result of the application of this reaction to other 16 kinds of substituted quinoline 1-oxides, it was proved that in all cases a CH3-SO2-group was introduced into the 2 or 4 position (when the 2 position was substituted) accompanied with the elimination of an oxygen atom from N→O group. The introduction of sulfonyl group into the 2 or 4 position was confirmed by reacting I or 2-phenylquinoline 1-oxide (I2) with S, ethane-(Sa), benzene-(Sb) or p-toluene-(Sc)-sulfonyl chlorides. In particular, the reaction of I2 was ascertained to produce a trace amount of 3-sulfonyl substituted compound. In this reaction step, sulfonyl chloride was first reacted with potassium cyanide to give sulfonyl cyanide, which was assumed to take part in the next step according to the following two pathways (Chart 3). (1) The reaction proceeds by nucleophilic attack of oxygen in N→O group on the carbon in -SO2-C≡N. (2) The sulfinic acid is first produced by an attack of CN- on the carbon in -SO2-C≡N and the reaction further proceeds. These assumptions were confirmed on the basis of the facts below. (A) In the reaction of p-toluenesulfonyl cyanide (Sc') with I or I2, p-tolylsulfonyl group is introduced into the 2 or 4 position. (B) Similar derivatives can be synthesized in good yield by the action of Sc and sodium p-toluenesulfinate (Sc") on I or I2. In case of I2, the reaction (B) afforded 3-substituted compound while the reaction (A) did not. However, when Sc"was added in the reaction (A), 3-substituted compound was also obtainable. Consequently it may be considered that this reaction proceeds mainly according to the pathway (2) accompanied with the simultaneous reaction of (1). The synthesis of 3-substituted compound will be reported in the other paper.