Synthesis and characterization of pyrimidyl- and pyrazinylselenium compounds: X-ray structure of 2,5-bis(methylselenenyl)pyrazine Jaspreet S. Dhau a,⇑ , Avtar Singh a , Amritpal Singh a , Rupy Dhir a , Paula Brandão b , Vítor Félix c a Department of Chemistry, Punjabi University, Patiala 147002, India b Departamento de Química, CICECO, Universidade de Aveiro, Aveiro 3810-193, Portugal c Departamento de Química, CICECO, and Secção Autónoma de Ciências da Saúde, Universidade de Aveiro, Aveiro 3810-193, Portugal article info Article history: Received 31 May 2014 Received in revised form 25 June 2014 Accepted 26 June 2014 Available online 4 July 2014 Keywords: Selenium Pyrimidine Pyrazine Lithiation abstract A methodology for the lithiation of pyrimidine (1a) was developed and used for the synthesis of pyrimid- ylselenium compounds. The procedure involved prior complexation of 1a with 2.2 equiv. of BF 3 Et 2 O fol- lowed by a reaction with LDA or LTMP. The pyrazinylselenium derivatives were synthesized from the direct lithiation of pyrazine (1b) as the BF 3 -directed lithiation failed to give the desired products. All the synthesized compounds were characterized by elemental analysis, NMR ( 1 H and 13 C) and Mass spectroscopy. In addition, 2,5-bis(methylselenenyl)pyrazine (9b) was characterized by single crystal X-ray crystallography. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction Organoseleniums with electron-deficient heterocycles have shown tremendous potential as biologically active agents [1–5], pre- cursors to semi-conducting materials [6–8] and synthons in organic synthesis [9,10]. The chemistry of pyridylseleniums has grown substantially in the last couple of decades [11–15], and that of pyrimidylseleniums has recently shown some activity [11,16–21]. Surprisingly, there is no report on the chemistry of pyrazinylseleni- um compounds. We are reporting here the synthesis and character- ization of pyrimidyl- and pyrazinylselenium compounds by a methodology that involves the lithiation of pyrimidine (1a) and pyrazine (1b), respectively. The direct lithiation of unsubstituted pyrimidine has always been a challenge due to the instability of the lithiated pyrimidine species [22], whereas that of 1b has been achieved with moderate success [22,23]. Recently, the BF 3 -directed metallation of substituted pyrimidines (2,4-dimethoxy-, 2-butoxy- pyrimidine, etc.) and pyrazines (2-chloro-, 2-bromopyrazine, etc.) has been reported with highly expensive bimetallic tetramethylpip- erdine (TMP) bases, TMPZnClLiCl and (TMP) 2 Mg2LiCl [24]. However, there is no report on the BF 3 -directed lithiation of 1a and 1b with lithium diisopropylamide (LDA) or lithium tetramethylpiperdide (LTMP). The present paper provides detailed investigation on the lithiation of 1a and 1b in the presence and absence of BF 3 Et 2 O with LDA and LTMP as the lithiating reagents, and selenium as the electrophile. 2. Experimental 2.1. General All the reagents and solvents were purified by standard proce- dures, and were freshly distilled prior to use [25]. LTMP and LDA were prepared by the reaction of n-BuLi with 2,2,6,6-tetramethyl- piperidine and diisopropylamine, respectively [26]. All the experi- ments were carried out in flame-dried round bottom flasks and under moisture-free nitrogen atmosphere. 1 H and 13 C NMR spectra were obtained on a Bruker 400 MHz spectrophotometer in CDCl 3 . 1 H NMR and 13 C NMR chemical shifts were cited with respect to tetramethylsilane as the internal standard. The EI mass spectra were measured using a Shimadzu GC-Mass Spectrometer equipped with an Rtx-1MS (30 m  0.25 mm ID  0.25 lm) capillary col- umn. Elemental analysis for C, H and N was carried out on a Vario MICRO Elementar analyzer. 2.2. 2-(Methylselenenyl)pyrimidine (4a) 1a (0.72 g, 0.70 mL, 9.0 mmol) was treated with a solution of BF 3 .Et 2 O in diethyl ether (2.81 g, 2.48 mL, 19.8 mmol) at 0 °C. The http://dx.doi.org/10.1016/j.ica.2014.06.025 0020-1693/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Present address: Electrical Engineering Department, University of South Florida, Tampa, FL 33647, USA. Tel.: +91 813 974 4787; fax: +91 813 974 2050. E-mail address: jassiv02@yahoo.co.in (J.S. Dhau). Inorganica Chimica Acta 421 (2014) 359–363 Contents lists available at ScienceDirect Inorganica Chimica Acta journal homepage: www.elsevier.com/locate/ica