J. Iran. Chem. Soc., Vol. 8, No. 1, March 2011, pp. 223-230. JOURNAL OF THE Iranian Chemical Society Synthesis of New Azines in Various Reaction Conditions and Investigation of their Cycloaddition Reaction R. Ranjbar-Karimi a, * and H. Loghmani-Khouzani b a Department of Chemistry, Faculty of Science, Vali-e-Asr University, Rafsanjan, Islamic Republic of Iran, P.O. BOX 77176 b Department of Chemistry, Faculty of Science, University of Isfahan, Isfahan, Islamic Republic of Iran (Received 25 April 2010, Accepted 9 July 2010) A series of new azines were prepared by reaction of 2-ketoalkyl quinoline derivatives with some hydrazone in solvent free reaction conditions using ultrasonic irradiation. The application of ultrasonic irradiation improved the yields and reduced the reaction times. These azines, due to having α-acidic hydrogen next to azine group and heterocycle ring, have tautomeric forms the degree of each of which was determined on the basis of 13 C NMR, 1 H NMR, UV and IR spectrum. The results revealed that all compounds exist mostly in the enaminone form. We attempted to obtain criss-cross or probably Diels-Alder cycloaddition products through the reaction of some of these new azines with 2-chloroacrylonitrile as a dienophile. Some new diene systems developed from the said reactions. Keywords: 2-Ketoalkyl quinoline, Azine, Tautomer, Criss-cross cycloaddition, Diels-Alder cycloaddition, Dienophile INTRODUCTION Azines are a class of compounds that have been receiving increasing attention in recent years for their antibacterial, antifungal and antitumor properties [1-2]. Azines have also been extensively used in bond formation reaction [3], polymerization [4], in the design of liquid crystal [5] and the synthesis of heterocyclic compounds [6-8]. Few studies have been done on the reaction of azines with dienophile. The pseudo-diene structure of azines is considered to be the main factor of the most interesting reactions of azines; and it is predictable that many of the reactions with dienes occur with azines as well. However, in comparison with an ordinary diene, the diene part of azines, which is in fact a hetero diene, acts differently. Due to the high electronegativity of nitrogen *Corresponding author. E-mail: karimi_r110@yahoo.com to carbon, the electron density around nitrogen is more than the carbon and the lone pairs of nitrogen also act as a sigma donor. One of the known reactions of azines is the criss-cross cycloaddition [9-10]. In this reaction, the dienophile containing electron withdrawing groups are added to an azine molecule and make two five-member cycles on two sides of N=N bond. Most of the aromatic aldazines have been used to produce this reaction but aliphatic or aliphatic-aromatic aldazine can not cause the criss-cross cycloaddition reaction. For instance, acetoneazine, in reaction with alkenes can not produce a criss-cross cycloaddition. But it has been established that hexafluoroacetoneazine, which is an electron poor azine, reacts with electron rich olefins or acetylene under heat or photochemical conditions and gives the criss-cross cycloaddition product in more than 80% yield [11]. Schimizu and co-workers have obtained the criss-cross