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

Hirao, Kazuyuki; ABE, E.; Yonemitsu, Osamu

doi:10.1016/s0040-4039(00)91193-6

Cited by 2 publications

(2 citation statements)

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“…Therefore, having succeeded in the generation and trapping of carbene 11 , we turned our attention to possible direct generation and trapping of alkyne 12 . To this end, ketone 20 was prepared as a mixture of isomers in 62% yield via diazomethane mediated one carbon ring expansion of bis-homocubanone 13 . Since experimental details are sketchy and all our attempts to fully separate the two regioisomers 20a and 20b failed, the mixture as such was subjected to gem-dibromination via hydrazones (Scheme ) .…”

Section: Resultsmentioning

confidence: 99%

“…To this end, ketone 20 was prepared as a mixture of isomers in 62% yield via diazomethane mediated one carbon ring expansion of bis-homocubanone 13 . Since experimental details are sketchy and all our attempts to fully separate the two regioisomers 20a and 20b failed, the mixture as such was subjected to gem-dibromination via hydrazones (Scheme ) . The product was a mixture of two components which were separated by preparative TLC.…”

Section: Resultsmentioning

confidence: 99%

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Generation and Trapping of a Cage Annulated Vinylidenecarbene and Approaches to Its Cycloalkyne Isomer

et al. 2012

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A novel cage-annulated (bis-homocubyl) vinylidenecarbene has been generated and successfully trapped without any intermediacy of its cycloalkyne isomer. The greater kinetic and thermodynamic stability of the vinylidenecarbene vis-à-vis its cycloalkyne isomer has been predicted by DFT B3LYP/6-31G* calculations. The calculated results suggest the prospects of the cycloalkyne becoming amenable for trapping, if generated under suitable experimental conditions, owing to the substantial kinetic energy barrier associated with its possible ring contraction via 1,2-shift to the vinylidenecarbene isomer and marginal ground state energy difference. However, all of our attempts to directly generate and trap the cycloalkyne yielded unsatisfactory results. Attempted generation and trapping of a C2-symmetric bis-vinylidenecarbene from a bis-vinylidenedibromide met with unexpected failure.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%