2,5-Diazabicyclo octenes

To Diazabicyclo[3.3.0]octadienes, Diazabicyclo 3.2.1 octadienes, and 2-Azabicyclo 3.2.1]octenes... 

However, the directed /3-metalation and derivatization of benzol[fc]-l, 4-diazabicyclo[2,2,2]octene has been successfully achieved, and in fact the whole process can be repeated next to the second nitrogen atom, provided that the initially added electrophile is stable to the metalation conditions (Scheme 150) (91KGS798). 

When the 2,3-diazabicyclo[2.2.2]-2-octene bears an endo-phenyl substituent, only the exo-face of the protonated diazene undergoes the cycloaddition of cyclohexadicnc affording the anti-isomer126. Conversely, an equimolar mixture of the anti- and syw-isomers is produced from the exo-phenyl-substituted diazene. 

Dimethyl azodicarboxylate (164) has been reported to undergo a [ 4 + 2] photocycloaddition to the diene (165) to give the 2,3-diazabicyclo[2.2.2]octene (166). An analogous solid-state addition has been described in the ox-azolone (167) to give the photodimer (IbS), and oxidation of the photoadduct derived from 1-oxoanhydromethylberberine and nitrosobenzene has been used in a synthesis of ring C-substituted benzo[c]phenanthridines. ... 

EMISSION YIELDS AND FLUORESCENCE LIFETIMES IN THE PHOTOLYSIS OF 2,3-diazabicyclo-[2.2.1]heptene-2 (BDH) and 2,3-diazabicyclo[2.2.2]octene-2... 

A second [4 + 2] cycloaddition of the diene system in 5 with excess of the alkene to yield 2,3-diazabicyclo[2.2.2]octenes 7. 

Hexafluoroacetone azine reacts with two equivalents of terminal olefins (71JCS(C)2404) and with acetylene derivatives (75TL1125), forming 1,5-diazabicy-clo[3.3.0]octenes and l,5-diazabicyclo[3.3.0]octa-2,6-dienes 27, respectively (Scheme 27). The cycloaddition involves two [3 + 2] processes. The structure of azamethineimine is confirmed by X-ray analysis data (74AGE475). 

Also the radical species are easily formed on treatment of l-ethyl-2,3-dicyano-1,4-diazinium [188, 189] and 1-ethyl-1,2,4-triazinium salts [190] with nucleophiles, as evidenced by dimerization of pyrazinyl radicals into the corresponding dimeric structure (Scheme 63). It is worth noting that the synthetic potential of the intermediate radicals can be used as trapped with compounds bearing C-C double or triple bonds, for instance by reacting with allyl carboranes. The latter reaction is accompanied by the hydrolysis of one cyano group and results in the formation of the corresponding 2,5-diazabicyclo[2,2,2]octenes (Scheme 63) [189]. 

A stirred and water-cooled soln. of 1,3-cyclohexadiene and diethyl azodi-carboxylate in cyclohexane irradiated 2 days under N2 with a 400 w. Hg-lamp diethyl 2,3-diazabicyclo [2.2.2]-5-octene-2,3-dicarboxylate. Y 87%. R. Askani, B. 98, 2551 (1965). 

Whereas diaza-compounds of type (639) decompose with concerted loss of nitrogen to 1,4-dienes, examination of the homologous diazabicyclo[4,2,0]octenes (640) reveals that they lose nitrogen non-concertedly without ring-closure, by a biradical mechanism. ... 

Tetrazines are widely used inverse electron-demand reagents in synthesis of both nitrogen-containing heterocycles (diazines), as well as tricyclic products containing diazabicyclo[2.2.2]octene skeleton. In analogy, corresponding less reactive 1,2,4-triazines produce pyridines and azabicyclo[2.2.2]octene skeleton. 

---