The present invention provides a novel, industrially realizable and economically preferable process for production of highly pure 1-benzyl-4-[(5,6-dimethoxy-1-indanon)-2-yl]methyl piperidine hydrochloride, i.e., donepezil hydrochloride shown in the following reaction scheme, in Polymorph (I) morphological crystal form. (I) In one of the key steps of the process, during the hydrogenation 5,6-dimethoxy 2-(pyridine-4-yhnethylene)indan-1-one hydrochloride is saturated using Pd carbon to get 4-[(5,6-dimethoxy-1-indanon)-2-yl]-methyl piperidine at more than 97% HPLC purity. In the crystallization step donepezil-hydrochloride is crystallized from an aqueous alcoholic solvent to get Polymorph (I) in at least 99.95% HPLC purity.
The present invention relates to a new process for the synthesis of high purity 3,5-diamino-6-(2,3-dichlorophenyl)-1,2,4-triazine of formula (I) using 2,3-dichlorobenzoyl cyanide and an aminoguanidine salt as starting materials. 2,3-dichlorobenzoyl cyanide is reacted with 1-2 mol equivalent of aminoguanidine salt in 3-6 mol equivalent of methanesulfonic acid, then the obtained adduct of formula (IV) is transformed without isolation into the product with magnesium oxide. In given case the obtained crude product can be recrystallized from a proper organic solvent ##STR00001##