N-(Cyclohex-1-enyl)-α-(methylthio)acetamides 1, upon treatment with Mn(OAc)3 in the presence of Cu(OAc)2, underwent cyclization in a 5-endo-trig manner to give 1,4,5,6-tetrahydro-3-methylthio-2H-indol-2-ones 2. The radical mechanism has been proposed for the cyclization of 1.
oxidation product 10. On the basis of these results, formation of 5 from 4 was thought to proceed via nucleophilic attack of the pyrrole ring on the cation-radical lX, generated by a single electron-transfer reaction of the acetoxy-substituted intermediate V. Treatment of compound 16 with Mn(OAc)3/Cu(OAc)2 gave no erythrinane derivative with recovery of the starting material, indicating that the presence