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The kinetic energy release T which accompanies the Br-loss from ionized (E)-and (Z)-0-bromostyrenes (5 and 6) in the gas phase is higher by 0.7 * 0.03 kcal mol-' than that from the molecular ion of a-bromostyrene (4). Together with both collisional activation (CA) spectra and MO calculations this is interpreted as evidence for the direct formation of the a-phenylvinyl cation 7 from 4' . and exothermic isomerization of the incipient [M -Br]' species formed from 5' . and 6' s. Except for collision-induced CH2 loss, the CA spectra of the C8H7+ ions formed from 4'-, 5'., and 6' . and by chemical ionization of henylacetylene are nearly identical. In the collision-induced methylene loss from the C8H7+ ions derived from a-and a partial degenerate isomerization prior to the CH2 loss. The various possible cationic intermediates from the dissociative ionization of 4-6 and the pathways connecting them were investigated computationally by MIND0/3 and ab initio methods. Only 7 and the phenyl-bridged ion 9 are stable species, while the 0-phenylvinyl cation 11 rearranges without activation energy via the hydrogen-bridged ion 10 to 7. The corrected STO-3G calculated relative energies in kcal mol-' are (7) 0, (9) 16, (10) 25, and (11) 42. The calculated barriers for the 11 -9 and the 7 -9 rearrangements are 4.4 and 32 kcal mol-'. MIND0/3 calculations show that p-OH and p-Me substituents have little effect on the energy differences between the a-aryl and the aryl-bridged vinyl cations. The T values associated with Br. loss from M' . of (E)-o-bromo-2,6-, -2,5-, and -3J-dimethylstyrenes are on the average 0.43 kcal mol-' higher than from the a-bromo analogues, indicating a similar isomerization to the more stable a-arylvinyl cations. The Tvalue for Br. loss from M'. of 2,2-dianisyl-l-phenylvinyl bromide (25) is 0.23 kcal mol-' higher than that for M+. of (E)-and (Z)-1,2-dianisyl-2-phenylvinyl bromides (23 and 24). Similar results are obtained for the 2,2-dianisyl-1-tolylvinyl and (Z)-1,2-dianisyl-2-tolylvinyl bromides (27 and 26). Exothermic isomerization of the a-phenyl and a-tolylvinyl cations to the a-anisylvinyl cations 28 and 29 is corroborated by CA spectra of the [M -Br]' ions. The loss of the An2C+-fragment from these ions is ascribed to a competition between the direct, collision-induced high-energy dissociation of 28 and 29, with a 0-aryl rearrangement prior to decomposition. Similarities and differences between the reactions of the vinyl cations in the gas and the condensed phase are discussed. 8-l P C-labeled 4 and 5, C, contributes 21.5% and C, 78.7% starting from 4, but C, contributes 29.9% starting from 5, indicating Many intrinsic properties of ions can be examined advantageously in the gas phase? For example, the number and structures of ionic species capable of existing in significant minima on the potential energy surface can be revealed by collisional activation (CA) mass ~pectrometry.~ Complementary information may be obtained from the kinetic energy release, T, which accompanies unimolecular dissociation of a m...

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Es werden die Synthesen der Thiazolo-und [1,31Thiazino[l,2,4]triazinone 3 -6 beschrieben. Die Darstellungen der Verbindungen 3 und 5 gelangen regiospezifisch mittels der Verbindungen 12 und 13. Syntheses of Thiazolo-and [1,3]Thiazinoll,2,41triazinonesThe syntheses of the thiazolo-and [1,3]thiazino[1,2,4]triazinones 3-6 are described. Preparations of compounds 3 and 5 were achieved regiospecifically by using the compounds 12 and 13.Die Arninotriazinone 1 und 2 sind gut bekannte Verbindungen rnit herbiziden Eigenschaften '). Wir haben die thiazolo-und [ 1,3]thiazinoanellierten Triazinone der Typen 3 -6 hergestellt und stellten fest, daR auch diese Verbindungen herbizid sind. Die wirksamsten Vertreter fanden wir in der Verbindungsklasse 3.Gemeinsarne Startrnaterialien der durchgefuhrten Triazinonsynthesen waren Glyoxylsauren und -ester (8, 9)*). Zur Darstellung von 3 und 4 wurden diese rnit Thiosemicarbazid zu den 3-Mercaptotriazinonen 73) und weiter mit 1,2-Dibromethan zu den Thiazolotriazinonen umgesetzt. Bei dieser Anellierung erhalt man in der Regel ein Gernisch der Regioisomeren 3 und 4, die sich jedoch saulenchrornatographisch leicht trennen lassen (Methode A)4'. Als Nachteil erwies sich, dalj die biologisch weniger aktiven lsomere 4 immer Hauptprodukte waren. Die Isomeren 3 entstanden nur als Nebenprodukte, oder -wie bei den Reaktionen der Methyl-und tert-Butyltriazinone 7a, bgar nicht.Regiospezifische Synthesen der Thiazolotriazinone 3 lieljen sich dann durch Umsetzungen der Glyoxylsauren 8 oder -ester 9 mit 2-Hydrazinothiazolin (12) (Methode B)') glatt realisieren. Analog konnten dann die [I ,3]Thiazinotriazinone 5 aus den Glyoxylsauren oder -estern mit 2-Hydrazino-5,6-dihydro-4H-l,3-thiazin (13) erhalten werden.Letzteres lien sich analog der Darstellung von 12@ durch Urnsetzung von Thiosemicarbazid rnit 3-Brompropylarnin-hydrobromid synthetisieren.Synthesen der ungesattigten Thiazolotriazinone 6 erfolgten auf folgendem Wege: Umsetzung der Glyoxylsauren 8 rnit Thiosemicarbazid zu den Sauren 10, Weiterreaktion rnit den entsprechenden a-Chlorcarbonylverbindungen zu den Thiazolhydrazinen 11 und schliel3lich Cyclisierung uber die gemischten Anhydride zu 6".

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