The Use of Switchable Polarity Solvents for the Synthesis of 16-Arylidene Steroids via Claisen–Schmidt Condensation

Ispán, Dávid and Szánti-Pintér, Eszter and Papp, Máté and Wouters, Johan and Tumanov, Nikolay and Zsirka, Balázs and Gömöry, Ágnes and Kollár, László and Skoda-Földes, Rita (2018) The Use of Switchable Polarity Solvents for the Synthesis of 16-Arylidene Steroids via Claisen–Schmidt Condensation. EUROPEAN JOURNAL OF ORGANIC CHEMISTRY (24). pp. 3236-3244. ISSN 1434-193X

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Abstract

Switchable polarity recyclable solvent mixtures were applied as reaction medium and catalyst to replace the conventional base catalysts in the Claisen–Schmidt condensation of 17-oxo steroids with aromatic aldehydes. Reversibility between ionic and nonionic forms of the new 2-n-butyl-1,1,3,3-tetramethylguanidine (nBu-TMG)/ethylene glycol/CO2 and 2-tert-butyl-1,1,3,3-tetramethylguanidine (tBu-TMG)/ethylene glycol/CO2 systems were proved by conductivity measurements. The structure of the ionic form was established by 1H NMR and IR measurements and by quantum chemical calculations. The steroidal products with androstane and estrane skeleton were characterised with spectroscopic methods (NMR, IR, MS).

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