Adamantane 1-halo

The reactions of 1,3-dihaloadamantanes with various carbanions in DMSO have been studied.18 For example, potassium enolates of acetophenone and pinacolone and the anion of nitromethane react with 1,3-diiodoadamantane (19) under photo-stimulation a free-radical chain process forms a 1-iodo monosubstitution product (20) as an intermediate, which undergoes concerted fragmentation to yield derivatives of 7-methylidenebicyclo[3.3.1]nonene (21). These and other results were interpreted in terms of the Srn1 mechanism. The work has been extended to the reactions of 1- and 2-halo- and 1,2-dichloro-adamantanes, examples of the SrnI mechanism again being found.19... 

It IS well known that adamantane or its 1-halo derivatives, for example 50, can be easily transformed into a stable tertiary 1-adamantyl cation 26. As was already mentioned vide supra), this cation owes its increased stability to the unique stabilization effects involving the participation of the remote centers in the charge delocalization. The pattern of NMR spectra may be used as a sensitive probe to the charge delocalization effects. Thus for the series of aliphatic tertiary carbenium ions, the presence of the positive charge induces a downfield shift of the H NMR signals (relative to those of the parent covalent precursor) at the adjacent centers. The magnitude of this effect decreases in the order S> y In the case of 26, a substantial downfield shift of -protons is also observed, but this effect is pronounced even stronger for the y-protons... 

Protoadamantanone is a versatile intermediate for the synthesis of not only protoadamantane derivatives,but also 1,2- and 2,4-disubstituted adamantanes, 2-substituted noradamantanes, and 4(5)-substituted 4-homoprotoadamantanes. 4-Protoadamantanone has been prepared by the nitrous acid deamination of 2-amino-l-adamantanol (77%), by aprotic diazo-tization of endo-7-aminomethylbicyclo[3.3.1]nonan-3-one in benzene with an equivalent amount of acetic acid (67%), and by thermolysis of 1-adamantyl hypohalites followed by base-promoted cyclization of the resulting halo ketones (32-37%).In spite of low and erratic yields, the last reaction sequence has provided the most convenient route to the protoadamantanes, since the other two approaches require lengthy syntheses of the starting materials. 

It is known that the introduction of adamantane fragments in epoxy polymers exercises an essential influence on their characteristics. In papers [19,20] the effect of such network structures is examined in the example of EP modified by adamantane acids. The interpretation of the results obtained in [19, 20] within the frameworks of the cluster model of the amorphous state structure of polymers [5, 6] allows to suppose availability of two types of clusters in the studied EP stable ones, formed by main chain segments, and unstable ones, formed at the expense of the interaction of adamantane fragments. The authors of papers [21-23] studied the problem of how much the indicated notions corresponded to the real structure of the studied EP. This can be carried out with the aid of the methods of [3], based on the study of wide angle X-ray halos. 

Study of the shape of the observed halos allows to establish [23] that their best description is reached in the assumption of the existence of two components of the amorphous halo for non-modified EP (EP-2) and two or three for EP containing adamantane fragments (EP-3 and EP-4) (Figure 5.4). The appearance of the third... 

As earlier, we attribute the halo component, which corresponds to the largest value of Bragg s interval with a loosely packed matrix. In this case d 2 and d characterise physical entanglements of the cluster network [23]. Since the values of d 2 for EP-2, EP-3 and EP-4 are sufficiently close (particularly at small modifier concentrations) then this parameter can be attributed to entanglements (clusters) formed by EP network segments. Then d corresponds to the network of physical entanglements formed at the expense of interaction of adamantane fragments [22]. 

In Figure 5.9 the dependences of the amplitude intensity of the third component of the amorphous halo and Bragg s interval value, corresponding to the entanglements network of adamantane fragments, on modifier contents are adduced. 

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