Syntheses and reactions of cage compounds VI. Synthesis of pentacyclo[6,3,0,02,7,05,11,06,9]-undecanones and pentacyclo[6,4,0,02,7,03,10,06,9]dodecanediones by diazomethane ring expansion
✍ Scribed by Ken-ichi Hirao; Etsuko Abe; Osamu Yonemitsu
- Publisher
- Elsevier Science
- Year
- 1975
- Tongue
- French
- Weight
- 232 KB
- Volume
- 16
- Category
- Article
- ISSN
- 0040-4039
No coin nor oath required. For personal study only.
✦ Synopsis
Cm irradiation, cyclopentadiene dimer (3 and its enone derivatives (L,s$ are converted easily to the corresponding cage compounds, 5, 16* 73and84 .." ,' u _, by intramolecular cycloaddition, whereas the corresponding transformation of a six-membered analog, from cyclohexadiene dimer (9_) to lO_, is not known. 5 Recently, the cage system of 2 was synthesized photochemically from cyclohexadienone dimers (g),6 and was interestingly found in a natural product. 7 Another synthesis of this cage system may be provided by ring expansion of kwith CH2N2. It is well known, however, that six-membered ring reacts with CH2N2 more rapidly than five-membered ring,' and accordingly it is difficult to synthesize six-membered ketones by this reaction, e.g., cyclopentanone gives primarily cycloheptanone rather than cyclohexanone. 9 This is also the case for the reaction of bridged bicyclic ketones 10 and usual cage compounds. 11 Nevertheless, the reaction of 2-5 can be expected to stop at the six-membered ketone stage, because homologous seven-membered ketones must have a quite large strain due to the cage system including bicyclo[2,2,0]hexane. hv