1.4- Diazocine, 1,4-dihydro structure

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... 

In contrast to the 1,4-dithiocin system, 1,4-dioxocin (1) is well-known and has been characterized as an olefinic compound by its spectra as well as its chemical behavior.5-6 The reason why 1,4-dioxocin in contrast to 1.4-dihydro-1.4-diazocine (see Section 1.4.) and 4//-l,4-oxazocinc (sec Section 1.12.), does not qualify as a 107r-aromatic species, is the less pronounced tendency of oxygen atoms for 7t-electron delocalization. An X-ray analysis of the 6-substituted 1,4-dioxocin 2 confirms the presumed nonplanar conformation of the 1,4-dioxocin structural element.9 The eight-membered ring exhibits a twisted boat-chair confirmation. 

Dihydro- 1,2-diazocines such as (183) have been referred to as l,2-diaza[8]annulenes (78AHC(23)55), and are of interest in connection with the potential aromaticity of the 107r-electron system provided by these rings (see Section 5.19.4.4). On the basis of UV and NMR data the dibenzodiazocine (183) was suggested to have a partially planar structure there is no direct evidence of aromatic character. 

In some respects, the nomenclature of 1,4-diazocines is similar to that for the eight-membered ring containing one nitrogen (82AHC115). The completely unsaturated compound, for which there exists two valence tautomeric structures, 5 and 6, is called 1,4-diazocine. The partially saturated derivatives are prefixed dihydro-, tetrahydro-, etc. The totally saturated compound is called perhydro-1,4-diazocine, or 1,4-diazacyclooctane. 

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