US 7,531,653 B2
	Manufacture of pure hydralazine salts
Jagadeesh B. Rangisetty, Lawrenceville, N.J. (US); Christopher N. Jobdevairakkam, Plainsboro, N.J. (US); and Jayaraman Kannappan, Plainsboro, N.J. (US)
Assigned to Navinta LLC, Ewing, N.J. (US)
Filed on Dec. 07, 2005, as Appl. No. 11/296,178.
Prior Publication US 2007/0129546 A1, Jun. 07, 2007
Int. Cl. C07D 237/30 (2006.01)

U.S. Cl. 544—237

9 Claims

1. A process of preparing purified hydralazine hydrochloride comprising the steps of: (a) reacting 1-2H-phthalazinone with less than about 3 mole equivalents of phosphorous oxychloride and then precipitating with a mineral acid or a strong organic acid in the presence of a first solvent to recover one or more 1-chlorophthalazine salts; (b) reacting the recovered one or more 1-chlorophthalazine salts with hydrazine hydrate and then precipitating hydralazine base by the addition of a second solvent; and (c) converting the precipitated hydralazine base to hydralazine hydrochloride in a third, organic solvent.