- Ring Expansion and Contraction of a Two-Carbon Bridged Spiropentane
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The reactions of tricyclo[4.1.0.01,3]heptan-4-one (5) and two related systems with diazomethane and m-CPBA were examined in order to determine the relative reactivity and migratory aptitudes for the three compounds. The reactions of 5 with diazomethane and m-CPBA yielded new derivatives of the tricyclo[5.1.0.01,3]octane ring system that showed that migration of cyclopropylcarbinyl is favored over cyclopropyl migration in this system. Photolysis of 5-diazotricyclo[4.1.0.01,3]heptan-4-one (23) in methanol and dimethylamine did not lead to ring contraction to the tricyclo[3.1.0.01,3]hexane ring system, but an interesting product was derived from an unusual rearrangement process in the photolysis in dimethylamine. Matrix photolysis of 23 at 15 K gave a decrease in the diazo band at 2085 cm-1 and the appearance of a new band at 2117 cm-1, which is a normal position expected for a small-ring ketene such as cyclopropylketene. Thus, matrix photolysis appears to have yielded a derivative of the previously unknown tricyclo[3.1.0.01,3]hexane ring system. The lithium enolate of 5 was characterized by NMR spectroscopy at -80 °C and was found to rearrange to m-cresol at -65 °C. The geometries of the bridged spiropentanes of this work were optimized at the MP2(frozen core)/6-31G* level of theory, and group equivalent values were derived in order to calculate the heats of formation for these compounds using the calculated energies.
- Wiberg, Kenneth B.,Snoonian, John R.
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p. 1390 - 1401
(2007/10/03)
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- Synthesis of 2-Substituted Bicyclopentanes from Bicyclohexan-2-one
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Bicyclohexan-2-one (1) was converted into the 3-diazo derivative (4) wich was ringcontracted thermally to give a variety of amides and esters of bicyclopentane-2-carboxylic acid as exo- and endo-stereoisomers.Conversion of the acids into the corresponding methyl ketones and then Baeyer-Villiger reaction has led to endo- and exo-bicyclopentan-2-yl acetates wich differed markedly in solvolytic reactivity.
- Brook, Peter R.,Brophy, Bernard V.
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p. 2509 - 2514
(2007/10/02)
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