Transannular rearrangements

Whereas exo-norbornene oxide rearranges to nortricyclanol on treatment with strong base through transannular C-H insertion (Scheme 5.11), endo-norbornene oxide 64 gives norcamphor 65 as the major product (Scheme 5.14) [15, 22]. This product arises from 1,2-hydrogen migration very little transannular rearrangement is observed. These two reaction pathways are often found to be in competition with one another, and subtle differences in substrate structure, and even in the base employed, can have a profound influence on product distribution. 

Table 5.7 Transannular rearrangement dependence on ring size.

Contemporaneously, Cope also reported the first examples of base-induced transannular rearrangements (C-H insertion) of medium-sized cycloalkene oxides 62 and 64 (Scheme 11) [48]. These transformations could proceed via a carbenoid species (the hthiated epoxide) and/or an a-alkoxy carbene (such as 57 in Fig. 2). 

In order to broaden the scope of asymmetric transannular rearrangement, functionalised raeso-epoxides derived from medium-sized cycloalkenes have been studied. Protected diol derivatives of cyclooctadiene oxide were used as the... 

The effect of different substitution on this transannular rearrangement was further studied on a range of disubstituted cyclooctene oxides. cis-4,7-Di(t-butyldimethylsilyloxy)-cyclooctene oxide 80 yielded a mixture of bicyclic alcohol 81, and alkene 82 arising from reductive alkylation [Eq. (28)] [61,62]. 

Acoxy compounds from ethers with transannular rearrangement Ethers from acoxy compounds... 

Ring expansion and ring division by transannular rearrangement s. 16, 212 ... 

The carbocationic polymerization of ND proceeds with transannular rearrangement, where both double bonds are involved. Thus, a product polymer has a rigid and high-Tg ( 320 °C) tricyclic repeat stmcture, suitable for thermoplastic applications. Peetz et al. examined cationic polymerization of ND using the 2-chloro-2,4,4-trimethylpentane (TMP-Cl)/TiCl4 initiating system. The use of a proton trap or an added base at -35 to -60 °C rendered the reaction controlled, and the inaeased linearly with conversion up to approximately 45%. The produrt polymer chain consisted of approximately equal amounts of exo/exo and exo/endo connected tricyclic repeat units. Furthermore, a set of three-arm star block copolymers, t-cumyl(PIB- -PND)3 and t-cumyl (PND-b-PIB)3, were prepared and characterized. ... 

The mercury(ii)-catalysed rearrangement of the cyclodeca-l,2,5,8-tetraene (51) in the presence of HOAc gives (52), (53), and an unassigned product. Transannular rearrangement via a mercury-carbene intermediate is favoured. ... 

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