FORM 2 THE PATENTS ACT, 1970 (39 OF 1970) & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION (See Section 10; Rule 13) TITLE PROCESS FOR THE PREPARATION OF DONEPEZIL HYDROCHLORIDE APPLICANT CIPLA LIMITED AN INDIAN COMPANY OF 289 BELLASIS ROAD, MUMBAI CENTRAL, MUMBAI - 400 008, MAHARASHTRA INDIA The following specification particularly describes the nature of the invention and the manner in which it is to be performed. PROCESS FOR THE PREPARATION OF DONEPEZIL HYDROCHLORIDE Field of the Invention The present invention relates to an improved process for the preparation of highly pure donepezil hydrochloride. More, particularly, the present invention relates to an improved process for the preparation of donepezil hydrochloride using a novel reduction step carried out using at least one hydrogenation catalyst, in the presence of ionic compounds in organic solvents or an aqueous solvent or mixture thereof from 1-benzyM-[5,6-dimethoxy-1-indanon-2-yl)rnethylene] pyridonium bromide. More particularly the invention relates to an industrially suitable process for the preparation of donepezil hydrochloride. Backqround of the Invention Donepezil hydrochloride, which is chemically known as 1-benzyl-4-[(5,6-dimethoxy-1-indanon)-2-yl)methyl piperidine hydrochloride [formula l] is used in the treatment of Alzheimer's disease where it is used to increase cortical acetylcholine. It is available for oral administration in film-coated tablets containing 5 or 10 mg of donepezil hydrochloride. Donepezil hydrochloride is well known in the art and was first disclosed in US patent no. 4,895,841, hereinafter referred to as the '841 patent. As described therein donepezil hydrochloride is prepared by reacting 5,6-dimethoxy-1-indanone with 1- benzyl-4-formyipiperidine in the presence of a strong base such as lithium diisopropyl amide followed by a reduction step (Examples 3 and 4) with a palladium carbon catalyst in tetrahydrofuran