Iodocyclization of 6-allylamino-4,5-dihydropyrazolo[3,4-d]pyrimidines

6-Allylamino-1-R-4,5-dihydro-1H-pyrazolo3,4-d]pyrimidines treated with iodine in the presence of potassium carbonate are converted into 6-allylamino-1-R-1H-pyrazolo3,4-d]pyrimidines that at further reaction with iodine undergo the cyclization into 6-iodomethyl-1-R-1,6,7,8-tetrahydroimidazo 1,2-a]pyrazolo3,4-d]-pyrimidin-5-ium iodide of a linear structure. In the absence of potassium carbonate alongside the mentioned linear products 8-iodo-methyl-1-R-1,4,5,6,7,8-hexahydroimidazo1,2-a]pyrazolo4,3-e] pyrimidin-9-ium iodides of an angular structure have been obtained.