Photochemie von Heterocyclen, 8. Zur Photoreaktion von 2,5‐Diaryl‐1,3,4‐oxadiazolen mit 1,3‐Dimethyluracilen. Eine neue einfache Synthese von 1,2,4,5‐Tetrazinen

Abstract

In Fortsetzung andere$ und eigener9) Arbeiten zur Cycloaddition geeigneter Doppelbindungssysteme an Uracile sowie an 6-Aza~racile'~) mochten wir iiber einige Resultate bei der Photoreaktion von 2,5-Diaryl-l,3,4-oxadiazolen mit 1,3-Dimethyluracilen berichten:Abweichend vom oben erwahnten R e a k t i~n s v e r h a l t e n~~~) der 1,3,4-Oxadiazole findet bei UV-Bestrahlung von 2a-g in Gegenwart von 1,3-Dirnethyluracil (la) keine

Nucleophile-Induced Intramolecular Dipole 1,5-Transfer and 1,6-Cyclization: Experimental and ab Initio Studies of Formation, Thermolysis, and Molecular and Electronic Structures of 3,6-Diphenyl-1-propanesulfenimido-1,2,4,5-tetrazine

“…The downfield absorption of a phenyl ring (8.36 ppm) resembles that observed for 5 (8.67 ppm). The resonance at 160.53 ppm, presumably the C 6 carbon in 1 (Scheme ), is similar to that ascribed to the C 3/6 carbon in diphenyltetrazine 5 (164.04 ppm) . The second low-field absorption at 145.78 ppm can be assigned to the C 3 carbon in 1 and shows a marked difference in chemical environments for the heterocyclic carbon atoms.…”

“…The UV spectrum of tetrazine ylide 1 consists of three bands at 368, 274, and about 200 nm, and a broad absorption band tailing to about 510 nm, which is responsible for the orange-yellow color of the compound (Figure ). This spectrum is markedly different from that of 2,6-diphenyl-1,2,4,5-tetrazine ( 5 ), which exhibits a weak transition at 544 nm (MeOH) in addition to a strong band at 294 nm …”

Donor−Acceptor−Donor Tetrazines Containing a Ferrocene Unit: Synthesis, Electrochemical and Spectroscopic Properties

“…The UV−vis spectra of compounds 4 and 5 were obtained in dichloromethane and are displayed in Figure . Electronic absorption data for 4 and 5 are collected in Table , along with those of the previously reported 3,6-bis(thien-2-yl)- s -tetrazine ( 6 ), 3,6-bisphenylyl- s -tetrazine ( 7 ), and the generic s -tetrazine ( 8 ) . Both tetrazines 4 and 5 show three bands, one in the UV and two bands in the visible range.…”

Poly[3,4‐dihydroxybenzhydrazide]: A Polydopamine Analogue?

“…Thus, the carbonyl group could undergo condensation reactions by elimination of water, for example, in the formation of 1,2,4,5‐tetrazines 6 . Such examples are reported for acylhydrazines . The hydrazine group of DHBH is strongly nucleophilic allowing condensation reactions, for example, hydrazone formation 7 as found in reactions of o ‐quinones with aryl hydrazines .…”