Manjunatha M. Ramaiah*, Nanjundaswamy Shivananju and Priya Babu Shubha Pages 1 - 9 ( 9 )
Titanium ethoxide has been employed as a novel and efficient reagent for the Knoevenagel condensation of aldehydes with active methylenes such as diethyl malonate and ethyl cyanoacetate under solvent free conditions to afford substituted olefins in high to excellent yields. The reaction is suitable for a variety of aromatic, aliphatic and heteroaromatic aldehydes with various active methylenes. Parallelly microwave irradiation has been utilized to achieve improved reaction rates and enhanced yields. Herein, we illustrated a convenient method for the preparation of α,β-unsaturated compounds using both conventional and microwave irradiation methods. Efficient and solvent free Knoevenagel condensation between aldehydes and active methylenes were developed using titanium ethoxide. The procedure was successful with a wide range of substrates such as aromatic, aliphatic and heterocyclic aldehydes and various active methylenes to afford substituted olefins. The reaction was also carried out under microwave irradiation to accomplish the corresponding olefins with improved reaction rates, yields and cleaner reaction profiles.We have developed an efficient and novel methodology for the synthesis of olefinic compounds by Knoevenagel condensation under solvent-free conditions using titanium ethoxide; for the first time as a reagent and solvent as well. This method is appropriate for the synthesis of a variety of aromatic aldehydes containing various electron-donating and withdrawing groups, aliphatic and heteroaromatic aldehydes. The significant advantages offered by this methodology could be applied to various active methylenes in order to offer the corresponding Knoevenagel products. Thus, we believe that this method delivers high conversions, cleaner reaction profiles under solvent-free reaction conditions and shorter reaction times, all of which make it a very useful and attractive approach for the preparation of wide range of substituted olefins.
Knoevenagel condensation, titanium(IV) ethoxide, aldehydes, active methylenes, solvent-free, conventional, microwave irradiation.
Department of Studies in Chemistry, University of Mysore, Manasagangotri, Mysuru, , Department of Biotechnology, Sri Jayachamarajendra College of Engineering, JSS Technical Institutions Campus, Mysuru, , Department of Studies in Chemistry, University of Mysore, Manasagangotri, Mysuru