Bicyclo octadiene synthesis

The synthesis of bicyclo[3.2.1]octadienes 86 has been accomplished by refluxing divinyl-cyclopropanes 85 in xylene. Subsequent research led to the development of conditions employing a rhodium-catalyzed step for the synthesis of bridged systems via the cyclopropanation of cyclopentadienes, furans and pyrroles (see section on transition-metal-mediated rearrangements). 

Several sesquiterpenes have been synthesized using this methodology. Bicyclo[3.2.1]octadiene 92, obtained in excellent yield from 91, has been used in the synthesis of prezizaene (93). Other targets included sinularene (94) and quadrone (95). ... 

TABLE 16. Synthesis of Bicyclo[3.1.0]hexanes Cyclization of 6-HaIo-l,6-octadienes and 1,6-Octenynes ... 

Another wonderful example of a related strategy implemented in a natural product synthesis is depicted in Scheme 6.24. The kingianins are a class of natural products which are homo- or heterochiral dimers of bicyclo[4.2.0]octadienes. These... 

The biomimetic 87t/67T -electrocyclization process was also applied in several other syntheses of natural products containing a bicyclo[4.2.0]octadiene structure. Parker and Lim [107] used a domino Stille/87r/67T -electrocyclization reaction for the total synthesis of the immunosuppressants SNF4435 C (267) and D (268). Interestingly, the ratio of SNF4435 C and D found in nature (2.3 1) is close to that obtained in the synthetic approach (Scheme 14.41). This indicates that an... 

Since the work reported by Carreira and coworkers [36] on the synthesis and application of other chiral-bridged dienes containing the bicyclo[2.2.2]octadiene scaffold, Hayashi s group [40] has developed further these diene-type ligands and applied them successfully in the 1,4-addition of phenylboronic acids to unsaturated enones. Some of the bicyclo[2.2.2]octadiene ligand derivatives and their products can be seen in Scheme 5.11. 

Bicyclo[2.2.2]octadiene-fused porphyrins 44 involving core-modified ones were prepared by the common preparation methods of porphyrin syntheses such as cyclic tetrameriza-tion, [3 + 1], and [2 + 2] methods, and were converted to tetrabenzo derivatives 45 by heating (Scheme 15.6). Because synthesis of the quadruply BCOD-fused porphyrins was thought to be more difficult than those of singly, doubly,... 

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