The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 06, 2011
Filed:
Dec. 21, 2006
Guanghui Tian, Shanghai, CN;
Yi Zhu, Shanghai, CN;
Zheng Liu, Shanghai, CN;
Zhen Wang, Shanghai, CN;
Jingshan Shen, Shanghai, CN;
Guanghui Tian, Shanghai, CN;
Yi Zhu, Shanghai, CN;
Zheng Liu, Shanghai, CN;
Zhen Wang, Shanghai, CN;
Jingshan Shen, Shanghai, CN;
Topharman Shanghai Co., Ltd., Shanghai, CN;
Abstract
The present invention discloses a process for preparing sildenafil and its intermediates having the structures outlined below: In particular, the present invention provides a process for preparing the compound of formula (I) and its intermediates, i.e. the compounds of formula (I), (II), (III) and (IV). The compound of formula (I) is obtained from the compound of formula (II); the compound (II) is obtained from the compound of formula (III) and methylpiperazine; the compound (III) is obtained by treating the compound of formula (IV) with chlorosulfonic acid; the compound (IV) is obtained though treating the compound of formula (V) in the presence of at least one selected from POX, PX, PXand their mixtures in any ratio. The process for preparing the compound of formula (I) according to the present invention reduces the side reactions in the processes of the prior art. These improvements lead to higher yields and a better industrial applicability with easier controlling of the reaction.