Claisen-Schmidt Condensation And Domino Claisen-Schmidt Condensation - Michael Addition Of 16-Formyl Steroids In The Presence Of Switchable Polarity Solvents

Switchable polarity solvents (reversible ionic liquids) have been used to replace conventional catalysts and solvents in Claisen-Schmidt condensation reactions of 16-formyl steroids and aromatic ketones. The primarily formed alpha,beta-unsaturated ketones may undergo a Michael addition with the aromatic ketone reaction partner. By the proper choice of the reaction conditions, either the alpha,beta-unsaturated ketone or the products of the domino Claisen-Schmidt condensation - Michael addition could be obtained with good selectivity. The catalyst could successfully be recovered and reused. The steroidal products with androstane and estrane skeleton were characterized by different spectroscopic methods (NMR, IR, MS).