Heterocycl. Commun., Vol. 18(1), pp. 29–31, 2012 • Copyright © by Walter de Gruyter • Berlin • Boston. DOI 10.1515/hc-2011-0058 Synthesis of new aza crown macrocycles and lariat ethers Sattar Ebrahimi 1, * and Hassan Moghanian 2 1 Department of Chemistry, Malayer Branch, Islamic Azad University, Malayer, Iran 2 Young Researchers Club, Dezful Branch, Islamic Azad University, Dezful, Iran * Corresponding author e-mail: seyonesi@gmail.com Abstract Aza crown macrocycles 3a,b were synthesized in good yield by condensation reaction of 1,3- and 1,4-bis(4-amino-5-mer- capto-4 H-1,2,4-triazol-3-yl)alkanes 1a,b with bis-aldehydes 2a,b. Reactions of 3a,b with methyl or benzyl iodide fur- nished the target lariat ethers 4a–d. Keywords: aza crown; lariat ether; macrocycle; 1,2,4-triazole. Introduction Incorporation of oxygen, nitrogen and sulfur atoms in the structure of macrocycles significantly affects their complex- ing properties because of the hard (O, N) and soft (S) char- acter of the donor atoms and the exodentate tendency of the sulfide linkages (Richard and Milton, 1976; Elwahy et al., 1996). Other changes involve the insertion of aromatic and/or heterocyclic ring systems into the macrocycles (Foroughifar et al., 2009a,b; Muathen et al., 2009). Heterocyclic groups provide rigidity and are able in some cases to form complexes via their soft donor atoms (Newkome et al., 1977). Extensive interest in the synthesis of macrocyclic compounds containing five- and six-membered heterocyclic rings as subunits has led to the preparation of a range of such compounds which have been shown to possess very interesting properties (Bradshaw et al., 1984, 1990; Ibrahim et al., 1999; Elwahy and Masaret, 2007). Lariat ethers are compounds with a macrocyclic ring and a side arm which bears a donor group (Elwahy and Abbas, 2008; Abbas and Elwahy , 2009; Sharghi et al., 2010). Such compounds have been designed as cation complexing agents which exhibit complexation behavior similar to crown ethers, but with a three-dimensional binding character (Weber and Vogtle, 1981). Lariat ethers can be divided into two catego- ries depending upon the nature of the secondary binding site: that with a pendent neutral side arm, and lariat ethers with a pendent proton-ionizable arm. Non-ionizable lariat ethers may exhibit an enhanced cation complexation and selectivity when compared to crown ethers without side arms (Kolthoff, 1979). Intensive development of the lariat crown ether concept has been directed towards the synthesis of several side- armed crown ethers, designed for uses ranging from routine (polymer-supported PTC catalysts, separation/extraction reagents, etc.) to sophisticated applications such as redox switches for membrane transport, synthetic cation conduct- ing channels, nucleotide-based molecular boxes (Gokel et al., 1980; Schultz et al., 1985). These valuable properties prompted us to synthesize new aza crown macrocycles fused with two 1,2,4-triazole rings containing the N and O atoms inside the macrocyclic ring as donor atoms and containing pendant thiol groups as precursors for the synthesis of lariat thioethers. Results and discussion In continuation of our interest to develop the synthesis of new macrocycles and lariat ethers (Foroughifar et al., 2009a,b), we report herein a simple and efficient method for the synthesis of new macrocycles 3a,b and lariat ethers 4a–d. The synthetic strategy includes cyclocondensation between bis-aminotriazoles and the appropriate bis-alde- hydes, to give the corresponding Schiff bases. The starting 1,2-bis(4-amino-5-mercapto-4 H-1,2,4- triazol-3-yl)alkanes 1a,b were prepared by heating aliphatic diacids with two molar equivalents of carbonothioic dihydrazide in an oil bath at 170°C (Xu et al., 1999). Reactions of 1,2-bis(4-amino-5- mercapto-4 H-1,2,4-triazol-3-yl)alkanes 1a,b with bis-alde- hydes 2a,b (Ibrahim et al., 1994) in acetic acid afforded the corresponding macrocyclic compounds 3a,b (Scheme 1). The desired compounds were obtained in reasonable yields. The functionalities in these aza crown ethers make them valuable precursors for the formation of different fused heterocyclic compounds. The available macrocycles 3a,b encouraged us to study their transformation into the lariat ethers. Thus, the new lariat ethers 4a–d with neutral side arms were prepared by reaction of aza crown macrocycles 3a,b with methyl or benzyl iodide at room temperature (Scheme 1). The desired compounds were obtained in good yields. The IR spectra of the bis(4-amino-5-mercapto-4 H-1,2,4- triazol-3-yl)alkane 2a,b show absorption bands at 3154 and 3281 cm -1 due to the NH 2 groups which are absent in the IR spectra of the aza crown compounds 3a,b. Similarly, the 1 H NMR spectra of the bistriazoles 2a,b show a broad signal at δ 5.56 attributed to the NH 2 groups which are not present in the spectra of compounds 3a,b. The absence of the IR absorptions for amino groups and the 1 H NMR signals for thiol groups clearly confirmed the formation of lariat ethers 4a–d.