Dibenzo diazocin-14-one

A number of the purported syntheses of dibenzo[f>,/][l,4]diazocines in the literature have to be revised and the structure of the products corrected.1 Instead of the expected 1,4-diazocine derivatives 1, isoindolobenzimidazoles 2 are actually isolated, the formation of which requires a hydride shift after transannular attack of one imine group onto the other. 

The unsubstituted parent 1,5-diazocine (1) is hitherto unknown. Benzannulated systems, however, have been prepared, particularly dibenzo f>,/][l, 5]diazocine and its derivatives which have been intensively investigated due to their pharmacological properties. So far, all compounds synthesized show no evidence for delocalization of the 7t-electrons. One special review on the chemistry of 1,5-diazocines is available.1... 

From the general structure of 1,2-diheterocines 1 with identical heteroatoms other than the scries with two nitrogen atoms (X — NR, which have already been discussed in Section 1.2. as they can be regarded as 1,2-dihydro-l, 2-diazocines), only one other example of such a 1,2-di-hcterocine system exists i.e. dibenzo derivative 4 containing the 1,2-dithiocin system 2.1... 

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>. 

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