Formation of the E-isomer as an impurity in the optimized flow synthesis of a Z-α-thio-β-chloroacrylamide; E/Z photoisomerization in batch and flow, and solid state characterization of both isomers

N-(4-Methylphenyl)-Z-3-chloro-2-(phenylthio)propenamide (Z-3), a compound valuable as a reactive substrate for a range of synthetic transformations, was obtained through a three-step process involving both batch and flow methodologies. The compound Z-3 was isolated as a crystalline material of high purity; however, the E-isomer, E-3, was observed to form in solid samples of Z-3 during storage. Increased ratios of E-3, as well as pure isolated samples, were produced by photoisomerization in both batch and flow modes, with the flow process being identified as optimal in terms of process time. Crystal structure analysis of both the Z and E isomers was carried out, and key differences in molecular conformations and supramolecular interactions were highlighted, with greater deviation from planarity being exhibited by E-3 relative to Z-3. Powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) analyses of Z-3 samples were conducted after recrystallization from a variety of solvents, and the resulting data were found to be consistent with the determined crystal structure of Z-3.

• Dennehy, O
• Lynch, D
• Khandavilli, U
• Lawrence, S
• Collins, S
• Maguire, A
• Moynihan, H

• School of Chemistry/Analytical and Biological Chemistry Research Facility/SSPC, The Research Ireland Centre for Pharmaceuticals/University College Cork, College Road, Cork T12 YN60, Ireland

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