Microwave Assisted Prospective Synthesis of New 5-Arylidene Rhodanine Derivatives Bearing a 3-[4-(3-Aminopropyl)piperazin-1-yl]propyl Side Chain

A series of (5Z) 5-arylidene 2-thioxo-1,3-thiazolidin-4-one derivatives 7(a-l) bearing a [4-(3-aminopropyl)piperazin-1-yl]propyl side chain in N-3 position was prepared using a solution phase protocol assisted by microwave dielectric heating. These new compounds were synthesized in four steps with overall yields ranging from 12 to 33% via a "one-pot two-steps" protocol based on Holmberg reaction followed by a stereocontrolled Knoevenagel condensation. The rhodanine intermediate 4' issued from Holmberg reaction under microwave was also isolated and identified by spectroscopic methods of analysis. The twelve deprotected products 7(a-l) have been obtained with a Z-geometry about their exocyclic double bond. All N-Boc intermediates 6(a-l) and deprotected rhodanine derivatives 7(a-l) issued from trifluoroacetic acid treatment have been characterized by 1H, 13C and HRMS.