Mass Spectra of New Heterocycles: XXV. Electron Ionization Study of N-[5-Aminothiophen-2-yl]thioureas

• Published in: Russian journal of organic chemistry 2023-05, Vol.59 (5), p.776-781
• Main Authors: Klyba, L. V., Sanzheeva, E. R., Nedolya, N. A., Tarasova, O. A.
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Fragmentation; Ionization; Mass spectra; Mass spectroscopy; Molecular ions; Organic Chemistry; Thioureas
• ISSN: 1070-4280; 1608-3393
• DOI: 10.1134/S1070428023050056

The electron ionization mass spectra of previously unknown N -(5-aminothiophen-2-yl)thioureas obtained in one preparative step from propargylamines and isothiocyanates were studied for the first time, and the main fragmentation patterns of these compounds were revealed. All the thienylthioureas studied form a molecular ion ( I rel 7–61%), whose common fragmentation pathway {except for N -[5-(diethylamino)thiophen-2-yl]- N , N '-diphenylthiourea} is the cleavage of the R 1 N–C(=S) bond to form an intense [ M – R 2 NHCS] + ion peak ( I rel 35–85%). The main fragmentation pathway of the molecular ions of N -[5-(diethylamino)thiophen-2-yl]- N , N '-diphenylthiourea is associated with the opening of the thiophene ring by the C 2 –S and C 4 –C 5 bonds. N -[5-(Pyrrolidin-1-yl)thiophen-2-yl]- and N -[5-(piperidin-1-yl)thiophen-2-yl]thioureas characteristically undergo intense specific rearrangements that reveal themselves in the occurrence of unexpected primary fragmentation pathways of the molecular ions, the main of which is the elimination of an N , N '-dimethylcarbodiimide molecule.