| 摘要 |
Pyridine and hydrocarbyl-substituted pyridines are prepared by heating an amine or imine with iodine in the vapour phase at 300-800 DEG C., the amine or imine having a sequence of a nitrogen atom and five carbon atoms, the carbon atoms being contained in one or two N-alkyl groups, or groups differing therefrom solely by partial carbon-carbon unsaturation, and bearing sufficient hydrogen atoms to permit cyclization with loss of hydrogen, or, in the case of a tertiary amine, a substituent of the N atom. Preferred reactants are primary and secondary amines and imines. The iodine may be generated in situ from a metal iodide, e.g. lead or cadmium iodide, and oxygen, which is added to the vapour of the amine or imine. The cyclization may be effected in the presence of a metal oxide which may be inert towards the by-product hydrogen iodide, e.g. alumina, silica, or which may react with hydrogen iodide, e.g. nickel, iron or manganese oxides; the resulting metal iodides may be heated in an oxidizing atmosphere to regenerate iodine. Examples relate to the preparation of pyridine and some picolines from a wide variety of amines and imines. |
