Synthesis, IR-, NMR-, DFT and X-ray study of ferrocenyl heterocycles from thiosemicarbazones. Part 21: Study on ferrocenes

Cyclization reactions of the thiosemicarbazones of formyl- and acetylferrocene and their S-methyl derivatives with DMAD afforded novel ferrocenyl-hydrazono-substituted thiazolones, one–one dimethylthiazole-4,5-dicarboxylate and 1,3-thiazin-4-one, N-ferrocenylimino-pyrimidones/imidazolones, one intermediate β-adduct and via oxidative cyclization, a ferrocenyl-1,2,4-triazole. Ring isomerization of 1,3-thiazin-4-ones to a 1,3-thiazolones was detected. The structure of the new compounds was established by IR and NMR spectroscopy, including HMQC, HMBC and DEPT measurements and supported with GIAO NMR calculations and controlled also synthetically by phase-transfer methylation. For three compounds the stereostructure was also proved by X-ray diffraction.

Graphical abstractThiosemicarbazone-based synthesis, IR and NMR characterization of ferrocenylalkyl-ydenehydrazono-substituted heterocycles were described. Two structures were supported by GIAO NMR calculations at B3LYP/6-311+G(2d,p) level of DFT. For three compounds the stereostructure was also proved by X-ray diffraction revealing non-bonding S–O and S–N interactions in a methoxycarbonylmethylene-substituted thiazolidinone. These interactions were also discernible in the optimized structures obtained by B3LYP/6-31G(d) and B3LYP/6-31G(2d) methods.Figure optionsDownload full-size imageDownload as PowerPoint slide