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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.
A Solvent-Free Protocol for the Green Synthesis of 5-Arylidene-2,4-thiazolidinediones Using Ethylenediamine Diacetate as Catalyst
