*Corresponding author. Phone: +351 253 604381: Fax: +351 253 678983: e-mail: mfox@quimica.uminho.pt 1 Synthesis of 1-amino-4-(2´-thienyl)phthalazine derivatives M. Manuela M. Raposo * a Ana M. B. A. Sampaio a and G. Kirsch b a Centro de Química, Universidade do Minho, Campus de Gualtar 4710-057 Braga, Portugal b Laboratoire d´Ingénierie Moléculaire et Biochimie Pharmacologique, UFR SciFA/Université de Metz 1, Boulevard Arago, Metz Technopôle, 57078 Metz Cedex 3, France Abstract- A synthesis of 1-amino substituted 4-(2´-thienyl)-phthalazines is described from halo- derivatives of 4-(2´-thienyl)-1-(2H)-phthalazinone 3. Keywords: Friedel-Craft´s acylation, 1-amino-4-(2´-thienyl)phthalazines. Introduction The practical interest upon phthalazine derivatives is based on their widespread applications [1-4]. Phthalazines, like others members of the isomeric diazine series, have found wide applications as therapeutic agents [2], [5-21]. Phthalazines are also commonly used as ligands in transition metal catalysis [22-26], as chemiluminescent materials [27-31] and for optical applications [32]. Despite their significance, there are only a limited number of routes for the synthesis of phthalazines. The most commonly employed approach is through o -disubstituted benzenes. Thus, condensation of 1,2-diacylbenzenes or their aldehyde counterparts with hydrazine derivatives gives 1,4-disubstituted- or the parent unsubstituted phthalazines, respectively [1-3], [5-7], [9-10], [12]. Recently, palladium catalyzed coupling reactions were also applied in the phthalazine series [33-34]. Guery et al [33] obtained several new phthalazine derivatives through Suzuki coupling. Due to the nature of the phthalazine nucleus, synthesis of new derivatives becomes an importante issue. There has been little reported in the literature concerning 4-thienyl substituted phthalazines [17-18], [35-36]. It was for that reason that we decide to synthesize new thienylphthalazine derivatives. In this paper we report the synthesis of new 1-amino-4-(2´-thienyl)phthalazine derivatives 5a-e from halo derivatives 4a-b of the phthalazinone 3. Compound 3 was