Mayer, K. K. and Dove, S. and Pongratz, H. and Ertan, M. and Wiegrebe, Wolfgang (1998) Electron impact induced fragmentation of 4-aryl-4,6,7,8-tetrahydro-1H,3H-quinazoline-2,5-diones. HETEROCYCLES, 48 (6). pp. 1169-1183. ISSN 0385-5414,
Full text not available from this repository.Abstract
The molecular ions (M+.) of 4-substituted aryl-4,6,7,8-tetrahydro-1H,3H-quinazoline-2,5-diones (Biginelli compounds) (2 - 18) decompose by loss of the substituents X of the phenyl group (X = o-F; o-, m-, p-Cl, Br, OCH,, CH,; 2,3-, 2,4-, 2,6-, 3,4-dichloro) giving rise to prominent (M - X-.)(divided by) ions at 70 and 12 eV, respectively. In the cases of o-Cl and o-Br substitution, the M+. is extremely unstable. In general, metastable M+. (1st ffr) eliminates preferably H-., that of 15 (2,6-dichloro), however, exclusively a chlorine atom. As corroborated by H-2-labelling, reversible Ii-migration from C-4 to the phenyl group takes place (1, la 1c). The collisional activation spectra of the (M - X-.)(+) ions of 3 (o-Cl) and 6 (o-Br) are identical but different from the indistinguishable spectra of the (M - X-.) + ions of 4 (m-Cl), 5 (p-Cl), 9 (o-OCH3), 11 (p-OCH3), and 14 (p-CH3). Semiempirical MO calculations (MOPAC 6.0, PM 3 Hamiltonian) of the M+. of all ortho-substituted derivatives support a close interaction of o-Cl and o-Br with the carbonyl oxygen, leading to elimination of these substituents and affording cyclic oxonium ions. In the other cases loss of X-. is explained as a consequence of 4-H migration to the phenyl group.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | RADICAL CATIONS; |
| Subjects: | 600 Technology > 615 Pharmacy |
| Divisions: | Chemistry and Pharmacy > Institute of Pharmacy > Pharmaceutical/Medicinal Chemistry I (Prof. Elz) |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 09 May 2023 09:26 |
| Last Modified: | 09 May 2023 09:26 |
| URI: | https://pred.uni-regensburg.de/id/eprint/49759 |
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