A model for a solvent-free synthetic organic research laboratory: click-mechanosynthesis and structural characterization of thioureas without bulk solvents
A model for a solvent-free synthetic organic research laboratory: click-mechanosynthesis and structural characterization of thioureas without bulk solvents
作者:Vjekoslav Štrukil、Marina D. Igrc、László Fábián、Mirjana Eckert-Maksić、Scott L. Childs、David G. Reid、Melinda J. Duer、Ivan Halasz、Cristina Mottillo、Tomislav Friščić
DOI:10.1039/c2gc35799b
日期:——
The mechanochemical click coupling of isothiocyanates and amines has been used as a model reaction to demonstrate that the concept of a solvent-free research laboratory, which eliminates the use of bulk solvents for either chemical synthesis or structural characterization, is applicable to the synthesis of small organic molecules. Whereas the click coupling is achieved in high yields by simple manual grinding of reactants, the use of an electrical, digitally controllable laboratory mill provides a rapid, quantitative and general route to symmetrical and non-symmetrical aromatic or aromatic–aliphatic thioureas. The enhanced efficiency of electrical ball milling techniques, neat grinding or liquid-assisted grinding, over manual mortar-and-pestle synthesis is demonstrated in the synthesis of 49 different thiourea derivatives. Comparison of powder X-ray diffraction data of mechanochemical products with structural information found in the Cambridge Structural Database (CSD), or obtained herein through single crystal X-ray diffraction, indicates that the mechanochemically obtained thiourea derivatives are pure in a chemical sense, but can also demonstrate purity in a supramolecular sense, i.e. in all structurally explored cases the product consisted of a single polymorph. As an extension of our previous work on solvent-free synthesis of coordination polymers, it is now demonstrated that such polymorphic and chemical purity of selected thiourea derivatives, the latter being evidenced through quantitative reaction yields, can enable the direct solvent-free structural characterization of mechanochemical products through powder X-ray diffraction aided by solid-state NMR spectroscopy.
1b-9b) were synthesized from their corresponding thiourea analogues (1-9). The synthesis pathway was confirmed by an X-ray crystallographic studies of 1a, 1b and 5a. Title derivatives were tested for their in vitro antitubercular activity against standard, "wild-type" and atypical mycobacteria. The highest therapeutic potential was attributed to isomeric N-(bromophenyl)tetrazoles 8a and 9a. Their growth-inhibitory