Electrophilic interaction of iodine with N-aIkyl-1, 4-dihydropyridines 1 in
the presence of secondary amines stereoselectively leads to the correspond
ing trans-2,3-diamino-1,2,3,4-tetrahydropyridines 2 in satisfactory yields
(79-94%); the method allows the synthesis of piperidine, pyrrolidine, morph
oline and piperazine derivatives.