Transannular polymerization

While ring-opening polymerization of camphorsultam was attempted futilely to prepare a new polymer containing a bicyclic structure and a new acidic sulfonamide group in the backbone [115b], radical cyclopolymerization was exploited in the synthesis of 193 nm alicyclic polymers (Fig. 79). Transannular polymerization to form polynortricyclene bearing tert-butyl ester was utilized in radical copolymerization with MA (Fig. 79) [275]. Radical cyclopolymer-... 

An isomerization of bonds occurs in the transannular polymerization of norbornadiene ... 

Intramolecular transfer reactions are possible with cationic polymerizations. This leads to an isomerization of the monomeric unit. Since the monomeric unit of the resulting polymer often cannot be produced by polymerization of the monomer or unimer of this polymer, reactions of this type are also referred to as phantom or exotic polymerizations. At low temperatures, the isomerization polymerization is preferred to normal propagation, and here two types can occur. An isomerization of bonds occurs in the transannular polymerization of norbornadiene ... 

The transannular polymerization of bicycIo[2.2.1]heptadiene yields a polymer containing nortricyclene units [Eq. (II-4)] 62,166,169). 

Thereby, the presence of tertiary monophosphines is critical, because both polymeric (26) and cyclic tetrameric (24 and 25) complexes can be obtained depending on the phosphine added to the reaction mixture. Furthermore, with some of the phosphines rapid decomposition and deposition of metallic silver occurs. In the macrocyclic molecules 24 and 25 a pair of silver atoms is bridged by two bis(l-imidazolyl)borate moieties, with a transannular Ag Ag distance of 8.61 A for 24 and 8.89 A for 25. The conformations of 24 and 25 are... 

It should be emphasized that these reactions involving two trifunctional reagents afford monomeric compounds in high yields instead of polymeric products. There is no question that the driving force of these reactions which generate the tricyclic silatrane skeleton is the formation of the transannular Si- —N bond. 

However, this restriction does not hold if the phosphazene ring is subjected to ring-strain by the presence of a transannular ferrocenyl group, as in structure 3.37 and reaction (13).26 Under these circumstances, polymerization takes place to give 3.38 even if no halogen atoms are attached to the phosphorus atoms, although the reaction is accelerated by the presence of catalytic quantities of (NPC12)3. 

In the presence of cationic initiators, these monomers polymerize via a transannular mechanism to give polymers of structures P2eai and P26bi for the bicyclo[6.1.0]non-4-ene, and dihalo-9,9-bicyclo[6.1.0]non-4-ene, respectively (Equation 33). 

To explain the reactivity of diallyldimethylammonium chloride, Butler (16) proposed a ring-closing mechanism. This type of polymerization has been called intra-intermolecular, transannular, and cyclopolymerization (the latter is the most common). Initial research in the area of cyclopolymerization indicated that six-member rings were produced (16-20) however. Brace (21, 22) showed in the mid-1960s that five-member ring formation was actually more common. Recent NMR studies (23-25) confirm these findings. 

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