Base mediated synthesis of a-aminated aroyl/acetylnaphthalenes through [4þ2] annulations Surjeet Singh a , Ismail Althagafi b , Pratik Yadav a , Rahul Panwar a , Abhinav Kumar c , Ramendra Pratap a, * a Department of Chemistry, University of Delhi, North Campus, Delhi 110007, India b Department of Chemistry, Umm Alqra University, Makkah, Saudi Arabia c Department of Chemistry, University of Lucknow, Lucknow, Uttar Pradesh 226009, India article info Article history: Received 31 May 2014 Received in revised form 27 September 2014 Accepted 29 September 2014 Available online xxx Keywords: Naphthalene Annulation Ketenedithioacetal Acridine abstract We have developed a base promoted simple, efficient and alternative approach for the synthesis of 4- amino-3-aroyl//heteroaroyl/acetyl-2-methylsulfanyl-naphthalene-1-carbonitriles by reaction of easily accessible 3,3-bis(methylthio)-1-aryl/heteroaryl/acetylprop-2-en-1-one and 2-cyanomethyl-benzoni- trile. Reaction of 1-(2-halo/methoxy-phenyl)-3,3-bis(methylthio)prop-2-en-1-one and 2-cyanomethyl- benzonitrile under basic conditions also afforded 6-(methylthio)-7-oxo-7,12-dihydrobenzo[c]acridine-5- carbonitrile along with usual product. Structure of the synthesized product has been confirmed by single X-ray crystallography. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Arylketones are well known for their use as a building block for the synthesis of various pharmaceutical and biologically important compounds. 1 They are also in use for dye, fragrance and agro- chemical industries. 2 a-Aminoaryl-arylketone and closely related skeletons are reported as antitubulin agents 3 and also exhibit better anti-proliferative activity against human cancer cell than colchi- cine. 4 Functionalized a-aminated-diarylketones were used as an intermediate for synthesis of various natural products and bi- ologically important compound, such as derivatives of quinazo- lines, 5 new class of homocamptothecins, 6 2-(aminoalkyl)- 2,3,3a,8-tetrahydrodibenzo[c,f]isoazole[2,3-a]azepine derivatives, 7 azaisoflavones, 8 central benzodiazepine receptor 9 and pyrazole containing class of GluN 2 C/GluN 2 D selective antagonist. 10 These compounds were also used for the synthesis of various compounds possessing electrochemical and photophysical properties. 11 a- Aminoaryl-arylketones were generally synthesized by Friedele- Crafts acylation. 12 For monoacylation, protection of amine group is necessary and also requires excess of Lewis acid. In literature, limited methodologies are available for synthesis of a-amino aryl- ketones, such as Ru (II) catalyzed intermolecular ortho amidation of aromatic ketones, 13 Pd-catalyzed carbonylative cross-coupling fol- lowed by hydrogenation, 14 Cu-catalyzed synthesis of aryl amines from aryl halides and ammonia. 15 1-Amino-2-aroylnaphthalenes were also synthesized by reaction of 1-amino-naphthalene-2- carbonitrile and aryl magnesium halide (Grignard reagent). 16 Ear- lier literature procedures require expensive metal catalysts, harsh reaction conditions and moisture sensitive reagents, which gave us impetus to develop new protocol for synthesis of highly function- alized 1-amino-2-aroyl-naphthalene. Recently, we have developed a new precursor 2-(1-cyano- 2,2-bis(methylthio)vinyl)benzonitrile for the synthesis of 1-amino- 2-aroyl/acetylnaphthalenes. Reaction of 2-(1-cyano-2,2- bis(methylthio)vinyl)benzonitrile with various acetophenones/ac- etone under basic conditions involves (5þ1) annulation to afford 1-amino-2-aroyl/acetylnaphthalenes in good to moderate yields (Scheme 1). 17 2. Result and discussion In search of an alternative route to achieve excellent yield, we planned to use 3,3-bis(methylthio)-1-aryl/heteroaryl/acetylprop- 2-en-1-one as a precursor (Scheme 1). 18 These precursors are well explored by Ila and co-worker for the construction of polycyclic aromatic system. 19 The required precursor 3,3-bis(methylthio)-1- aryl/heteroaryl/acetylprop-2-en-1-ones was synthesized by re- action of various acetophenones, acetone or cyclopropylmethyl * Corresponding author. Tel./fax: þ91 27666646; e-mail address: ramen- drapratap@gmail.com (R. Pratap). Contents lists available at ScienceDirect Tetrahedron journal homepage: www.elsevier.com/locate/tet http://dx.doi.org/10.1016/j.tet.2014.09.089 0040-4020/Ó 2014 Elsevier Ltd. All rights reserved. Tetrahedron xxx (2014) 1e6 Please cite this article inpress as: Singh, S.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.09.089