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

Abstract

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···X (X = N, O, π) and π···π 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.