Patent ID: 7524861

Claim:
A process for producing a hydrate of an acid addition salt of a compound of formula (I): wherein R 11 and R 21 , which may be the same or different, are each hydrogen or alkoxy; R 31 and R 41 , which may be the same or different, are each independently selected from H, C 1 -C 6 alkyl, CF 3 , a halogen, NH 2 , NO 2 , NHOH, C 1 -C 6 alkoxy, hydroxy and phenyl; or R 31 and R 41 , when situated on adjacent carbon atoms, form together with the carbon atoms to which they are attached a benzene ring or a methylenedioxy substituent; R 51 is a group selected from pyridine, quinoline, isoquinoline, 5,6,7,8-tetrahydroquinoline and 5,6,7,8-tetrahydroisoquinoline, the group being unsubstituted or substituted by C 1 -C 6 alkyl or C 1 -C 6 alkoxy; r is 0 or 1, and s is 1, 2, or 3; which process comprises: (a) combining, in any order, a compound of formula (I) as defined above, a pharmaceutically acceptable organic solvent, an excess of water and a pharmaceutically acceptable strong acid to form a mixture; (b) warming the mixture until a clear solution forms; (c) filtering the solution while it is warm, to yield a filtrate; and (d) recovering the hydrate as defined above from the filtrate.