Zinc Tetrafluoroborate-Mediated Ring Expansion of trans-Aziridine-2-carboxylates to cis-2-Iminothiazolidines and cis-Thiazolidine-2-iminium Tetrafluoroborates and Evaluation of Antimicrobial Activity.

Cis-2-iminothiazolidines and cis-thiazolidine-2-iminium tetrafluoroborates were successfully produced from trans-N-alkyl aziridine-2-carboxylates and phenyl/alkyl isothiocyanates mediated by zinc tetrafluoroborate in refluxing DCE. Reactions were performed via a complete regio- and stereoselective process to give the title iminothiazolidines and cis-thiazolidine-2-iminium salts in moderate to good yields (35 to 82%) with a wide substrate scope. In addition, the antibacterial activity evaluation of these compounds, as well as the minimum inhibitory concentration (MIC) determination, revealed that only four cis-thiazolidine-2-iminium salts showed growth inhibition against Bacillus cereus.

Crystal structure of ethyl 2-(4-chlorophenyl)-3-cyclopentyl-4-oxo-1-propyl-imidazolidine-5-carboxylate.

The title compound, C20H27ClN2O3, was obtained via an original synthesis method. The central heterocyclic ring adopts a shallow envelope conformation, with the N atom bearing the cyclo-pentane ring as the flap [deviation from the other atoms = 0.442 (2) Å]. The cyclo-pentane ring adopts a twisted conformation about one of the CN-C bonds: the exocyclic C-N bond adopts an equatorial orientation. The dihedral angles between the central ring (all atoms) and the pendant five- and six-membered rings are 10.3 (2) and 87.76 (14)°, respectively. In the crystal, C-H⋯O inter-actions link the mol-ecules into [011] chains. A weak C-H⋯Cl inter-action links the chains into (100) sheets. A mechanism for the cyclization reaction is proposed.