Polycyclopentanoids

The analogous rearrangement of the bicyclooctenone in (3.28) gives a product which serves as a synthon for polycyclopentanoid terpenes and... 

Bicyclo[2.2.2]octen-2-ones 25 afford tricyclo[3.3.0.0 ]octan-3-ones 26 in very good to excellent yields. Quantum yields for these conversions are in the range 0.5-1.0. The products have been used as building blocks in the synthesis of polycyclopentanoid terpenes and prostacyclin ana-logues. 2" - "... 

A full report has been published on the chemistry of the highly functionalized bicyclo[3.2.0]heptene (90), reaction of which with diazoethane gives a mixture ica. 7 3) of the useful ring-expanded products (91) and (92). A synthesis of another potential precursor (93) of polycyclopentanoids has also been reported. ... 

Another example of the acid-catalysed intramolecular cyclization of diazoketones cf. refs. 58, 92, 93) is a high-yielding preparation of polycyclic enones (101) from diazoketones (100). Further reports have appeared on the preparation of fused cyclopentanones by condensations between acetonedicar-boxylate and a-diketones yields are higher if the substituents on the latter substrates are small. An alternative approach to polycyclopentanoids, consisting of successive additions of propargyl alcohol anions to cyclopentanones followed by double dehydrative cyclization and hydrogenation, has been used to prepare the potential dodecahedrane precursor (102) cf ref. 63). The cage compound (103), obtained from 1,4-naphthoquinones and cyclopentadiene, produces the polycyclopentanoid (104) under acyloin condensation conditions. ... 

Demuth, M., Raghvan, P.R., Carter, C., Nakano, K., and Schaffner, K., Photochemical high yield preparation of tricyclo[3.3.0.0 ]octan-3-ones. Potential synthons for polycyclopentanoid terpenes and prostacyclin analogs, Helv. Chim. Acta, 63, 2434,1980. 

Singh, V.K., Deota, RT., and Bedekar, A.V., Studies in the synthesis of polycyclopentanoids synthesis, oxa-di-7i-methane rearrangement of annulated bicyclo[2.2.2]octenones and cyclopropane ring cleavage of tetracyclo[6.3.0.0. > 0 > ]undecenones,/. Chem. Soc., Perkin Trans. 1, 903,1992. 

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