A Facile, Efficient and Solvent-Free Titanium (IV) Ethoxide Catalysed Knoevenagel Condensation of Aldehydes and Active Methylenes

: 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. Parallel to this, 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. An efficient and solvent free Knoevenagel condensation between aldehydes and active methylenes was developed using titanium ethoxide. The procedure proved to be 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 as well as a solvent. 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 a wide range of substituted olefins.

FT-Raman Spectroscopic Investigations of Titanium Alkoxides with Polymerizable Organic Ligands

Chelating agents are frequently used in sol-gel chemistry to decrease hydrolytic reactivity and uncontrolled precipitation of titanium alkoxides. The use of polymerizable organic compounds as chelating agents allows for the formation of copolymers consisting of hybrid inorganic/organic networks. The main task of this study was the analytical characterization of new molecular precursors and organically modified titanium oxide films. Methacrylic acid, itaconic anhydride, isoeugenol, and 2-acrylamido-2-methylpropane sulfonic acid were reacted with titanium isopropoxide and titanium ethoxide to form the corresponding chelated alkoxide sols. Thin sol-gel films of these compounds on metal substrates were prepared by dip-coating and studied by Fourier transform (FT) Raman spectroscopy. The spectra were compared to those of the precursors. By means of their characteristic vibrational bands, the presence of polymerizable groups was detected in the coatings. The systems investigated are capable of acting as adhesive promoters in dental applications.