Dibenzo diazocine-6,12-dione

Benzodiazocine and dibenzo[Z>,/][ 1,4]diazocine-diones (220) and (218) are obtained by condensation of diethyl succinate and phthalate, respectively, with o-phenylenediamine (69JOC2138). Contrary to an early report, the use of phthaloyl chloride leads to other products and not the tricyclic diazocine. The dibenzo derivative is also formed in the oxidation of diazabiphenylene (219) (78T495). Ring contraction of (218) occurs readily on heating or on treatment with PCI5 or with base. 

Several dibenzo[e,g][l,4]diazocines 4 have been prepared by the condensation of biphenyl-2,2 -diamine derivatives 3 with 1,2-diones. The reaction proceeds upon simply melting the two components together, or byluxing in a high-boiling solvent. 

To a solution of dibenzo[6,/][l, 4]diazocine-6,l (5H. 2H)-dione (7 1.7 g, 7.5 mmol) in morpholine (10 mL) was added dropwise a cooled solution of TiClj. (3.13 g, 16.5 mmol) in anisole (10 mL). The mixture was then heated at 125 C for 2.5 h. poured into ice and extracted with CHC13. The organic layer was dried (Na2S04), concentrated in vacuo, and the residue passed through a column of neutral alumina (CHC13/ MeOH 95 5) yield 1.92 g (68 %). An analytical sample was obtained by recrystallization (CH2Cl2/ petro-leum ether) as a gray solid nip 240-243 C. 

If the reaction is carried out at higher temperatures with longer reaction times, the primarily formed product is reportedly transformed to an alternative dibenzo-1,5-diazocine, i.e. dibenzo-[A,g][l,5]diazocine-5,7(6//,12//)-dione (3).51... 

Treatment of dibenzo[A,/][l, 5]diazocine-6,12(5//,l l/7)-dione (2) with phosphorus pentachlor-ide transforms the amide functions into imidoyl chloride moieties.57... 

The enantiomerization of 6,7-dihydro-dibenzo[///][l,2]diazocine-5,8-dione 2 was investigated using quantum-mechanical methods. At the density functional theory (DFT) B3LYP/6-31G(d,p) level, two enantiomeric -symmetric transition states (TSs) and two enantiomeric pathways were found with a calculated barrier of 155.6 kj mol-1. The pathways can be divided into two steps one involving primarily inversion of the amidic bridge and the other movement of the aromatic rings <2004TA537>. 

The 1,2-dioxocin ring system has received a rather surprising amount of attention, at least in relation to the other compounds discussed in this chapter (with the exception of the 1,2-diazocines). The vast majority of these reports deal with essentially two compounds, namely the 5,8-dialkoxy-5,8-dihydro-dibenzo[fi /][l,2]dioxocins (50) obtained from the ozonolysis of phenanthrene, and the corresponding 5,8-dione (51) ( diphenoyl peroxide ), but a substantial number of other derivatives have also appeared since the publication of CHEC-I in which only a single derivative was reported. 

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