A continuous process strategy has been developed for the preparation of α-thio-β-chloroacrylamides, a class of highly versatile synthetic intermediates. Flow platforms to generate the α-chloroamide and α-thioamide precursors were successfully adopted, progressing from the previously employed batch chemistry, and in both instances afford a readily scalable methodology. The implementation of the key α-thio-β-chloroacrylamide casade as a continuous flow reaction on a multi-gram scale is described, while the tuneable nature of the cascade, facilitated by continuous processing, is highlighted by selective generation of established intermediates and byproducts.

α-Thio-β-chloroacrylamides are of considerable synthetic utility due to their versatile reactivity profile enabling a diverse range of useful transformations. Availability of accurate and extensive solubility data and models is a prerequisite for advanced process optimization of such valuable pure synthetic intermediate compounds, in particular facilitating their isolation with a high degree of efficiency and control. As an illustrative example the solubility of one such derivative, N-(4methylphenyl-Z-3-chloro-2-(phenylthio)propenamide (Z-1), is described in the present work. Solubility data is reported in 12 pure solvents specifically selected for their potential utility in synthesis and isolation at scale. Solubility data are determined using the gravimetric method across a range of temperatures T= (278.15 to 318.15) K under pressure of 0.1 MPa. On a molar basis, the solubility of Z-1 at temperature T = 298.15 K was observed to follow the order: tetrahydrofuran > 1,2-dichloroethane > 2-methyltetrahydrofuran > butanone > acetone > ethyl acetate > methyl acetate > toluene > tert-butyl methyl ether > acetonitrile > 2-propanol > 2-methyl-2-butanol. The experimental solubility data were correlated by the modified Apelblat, Margules, Van-Laar, Wilson, and nonrandom two-liquid (NRTL) models. The NRTL model was found to result in the lowest error for 8 of the 12 solvents tested. In the case of acetonitrile, the Wilson model had a slightly lower mean square error of 3.52 × 10 −4 while for methyl acetate and 1,2-dichloroethane the Van-Laar model had the smallest mean square error of 1.47 × 10 −3 and 3.54 × 10 −4 , respectively. The provision of solubility data and models for such a prized and versatile compound will assist with further development of continuous isolation strategies.

Use of continuous flow processing to undertake a multistep chlorination cascade has been achieved with effective inline workup and end-of-line crystallization in batch, leading to isolation of α-thio-β-chloroacrylamide Z-3 in pure form from a complex reaction mixture, exploiting the advantage of efficient heat transfer in flow. During development of a continuous flow strategy for production of appreciable quantities of α-thio-β-chloroacrylamides, difficulties surrounding a labor and resource intensive workup followed by final product isolation were addressed. A greener solvent choice was applied to the chemical synthesis, which enabled inline purification and separation, resulting in the crystallization of pure product directly from the reaction mixture. This process was readily scalable and demonstrated control over impurity formation and removal, which is key in an industrial setting.