A series of monoalkylpyrazines have been chlorinated specifically in the 3-position with sulphuryl chloride in the presence of NN-dimethylformamide ; the nucleus of symmetrical 2.6-dialkylpyrazines is also readily chlorinated.The structures of the by-products from some of the reactions have been assigned. The reaction of isobutylpyrazine with phosphoryl chloride and phosphorus pentachloride was also investigated and gave specifically 2-chloro-5isobutylpyrazine in 25% yield. Bu': 0.93 (6H, d, J 6.5), ca. 2.00 ( l H , complex m), ca. 2.43 (2H, complex d) Bu': 0.90 (6H, d, J 6*5), ca. 2.03 ( l H , complex m), ca. 2.53 (2H, complex d) CH,:CEt: 1-5 (3H, t, J 7), 2-63 (2H, q, J 7, m, J ca. 1.5), 5.29 ( l H , d, J ca. 1.5, t, J ca. Bu*: 0.85 (3H, t, J 7), 1-31 (3H, d, J 7), ca. 1-4-2.0 (2H, complex m), 2-78 ( l H , sext, J 7) MeCHXMe: 1-87 (3H, d, J 7, m, J ca. 1.5), 2.08 (3H, m, J ca. 1.5), 6.49 (IH, q, J 7, q, 1*5), 5.80 ( l H , m, J < l ) f CU. 1.5) Bi8: 0-84 (3H, t , J 7), 1.28 (3H, d, J 7), ca. 1.4-2.0 (2H, complex, m), 2.77 (lH, sext)sulphuryl chloride appeared to be 1 : 1.2, and any amount yield) were isolated, and analogous products with an of NN-dimethylformamide in excess of 0.25 mol. equiv. unsaturated side-chain were also obtained from s-butylseemed to be superfluous but not detrimental to the pyrazine using an excess of sulphuryl chloride. reaction. It was also found that temperatures between Addition of aluminium chloride-sulphur mono-0 and 45" gave essentially the same yields (ca. 40% chloride (l%), which is known to catalyse the nuclear based on converted starting material over 1-3 h). chlorination of toluene by sulphuryl chloride,16 failed to *part from the main product, the Of s-butylpyrazine with an excess of sulphuryl chloride 16 I. L. Finar, '
