Catalyst-Free Synthesis of Novel 4-(Benzofuran-2-yl)-N-phenylthiazol-2(3H)-imines, Crystal Structure Elucidation, and the Effect of Phenyl Substitution on Crystal Packing

A one-pot reaction of an equimolar mixture of 4-methoxyaniline, phenyl isothiocyanate, and 2-bromoacetylbenzofuran in absolute ethanol in the absence of any catalysts afforded 4-(benzofuran-2-yl)-3-(4-methoxyphenyl)-N-phenylthiazol-2(3H)-imine with an 83% yield. Under similar conditions, 4-flouroaniline provided a mixture of the expected 4-(benzofuran-2-yl)-3-(4-fluorophenyl)-N-phenylthiazol-2(3H)-imine and unexpected 4-(benzofuran-2-yl)-N-(4-fluorophenyl)-3-phenylthiazol-2(3H)-imine at an overall 73% yield. The structures of the synthesized heterocycles were confirmed using NMR spectroscopy. The products were recrystallized from dimethylformamide to afford samples suitable for structural determination via single-crystal diffraction. The molecules of the products share a common backbone and have similar conformations. They also display some common intermolecular interactions, including C-H & BULL;& BULL;& BULL;X (X = N, O, p) and p & BULL;& BULL;& BULL;p contacts. The molecules differ due to the methoxy and fluoro substituents on their phenyl rings, resulting in variations in the extended network in the crystals. Electron density maps and Hirshfeld surfaces have been used to rationalize the intermolecular contacts.

Automated summary

A one-pot reaction was performed without any catalysts to react 4-methoxyaniline, phenyl isothiocyanate, and 2-bromoacetylbenzofuran in absolute ethanol, resulting in a yield of 83% for the synthesis of 4-(benzofuran-2-yl)-3-(4-methoxyphenyl)-N-phenylthiazol-2(3H)-imine. Under similar conditions, a mixture of 4-(benzofuran-2-yl)-3-(4-fluorophenyl)-N-phenylthiazol-2(3H)-imine and 4-(benzofuran-2-yl)-N-(4-fluorophenyl)-3-phenylthiazol-2(3H)-imine was obtained from the reaction of 4-fluoroaniline with a overall yield of 73%. Structural determination of the products was conducted using single-crystal diffraction after recrystallization from dimethylformamide.