Novel parallel reaction between a [1,5] sigmatropic alkylthio shift and a [1,5] sigmatropic hydrogen shift observed in a 2H-azepine ring

Although heating 2-methoxy-2H-azepine results in a 1,5] sigmatropic hydrogen shift, heating 2-propylthio-2H-azepine results in not only a 1,5] sigmatropic hydrogen shift but also a 1,5] sigmatropic propylthio shift. Kinetic measurements reveal that migratory aptitudes increase in the order of MeO < H, PrS. These 1,5] sigmatropic shifts are discussed on the basis of ab initio DFT calculations. reaction: see text].