Circumambulatory 1.3-shifts

Another possible reaction, namely circumambulatory 1,3-shifts of the C5 carbon in BCP have not been observed except with carbomethoxy and cyano substitution. 

Note that the first example bears out the stereochemical prediction made earlier. Only the two isomers shown were formed. In the second example, migration can > continue around the ring. Migrations of this kind are called circumambulatory rearrangements. Such migrations are known for cyclopentadiene, pyrrole, and phosphole derivatives.[1,5] Hydrogen shifts are also known with vinyl aziridines." ... 

Hart and Kusuya have documented the remarkable properties of the nona-methylbicyclo[3.2.1]octa-3,6-dien-2-yl cation (75) as generated by ionization of the alcohol in magic acid.127 Below —60 °C in this solvent system, 75 undergoes both a rapid circumambulatory process (NMR observable) and a slower bridge shift (deuterium labelling necessary for observation). At or above -60 °C, 75 rearranges irrever-... 

Benzene oxides also undergo circumambulatory 1,5-oxygen shifts. Finally, the conversion of benzene oxide to phenol was proposed and subsequently found to proceed via an acid-catalyzed reaction part of which involves an intermediate diol. " ... 

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