1978 Volume 51 Issue 12 Pages 3599-3605
Several N-acyl-S,S-arylphenylsulfilimines were prepared and subjected to thermal decomposition. They decomposed readily at 130–190 °C to give isocyanates together with diphenyl sulfide, quantitatively. However, N-tosyl-S,S-diphenylsulfilimine did not decompose even upon heating at 200 °C for 24 h. A kinetic study revealed that the rates of pyrolysis of N-aroyl-S,S-arylphenylsulfilimines (p-Y–C6H4(Ph)S→NCOC6H4–X-p) are nicely correlated with the Hammett σ-values, ρX=−1.2 and ρY=+0.92, respectively, being obtained. The activation enthalpies and entropies were ΔH\ eweq=38.7 kcal/mol and ΔS\ eweq=6.0 e.u. for Ph2S→NCOPh and ΔH\ eweq=32.3 kcal/mol and ΔS\ eweq=5.5 e.u. for (Remark: Graphics omitted.), respectively. The rearrangement was accelerated considerably by o-methyl substituent in the aryl group. The effect of solvent on the rate of pyrolysis was small. The results indicate that the pyrolysis of sulfilimine proceeds via a concerted migration of the R group from carbonyl carbon to imino nitrogen similar to the Curtius type rearrangement of acid azide.
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