Cyclopentanone alkanone

Intramolecular carbene C-H insertion frequently leads to the formation of five-membered rings [967,990,1021,1113-1128], In particular l-diazo-2-alkanones tend to yield cyclopentanones exclusively when treated with rhodium(ll) carboxylates. The use of enantiomerically pure catalysts for diazodecomposition enables the preparation of non-racemic cyclopentane derivatives [1005,1052,1074,1092,1129]. Intramolecular 1,5-C-H insertion can efficiently compete with 1,2-C-H insertion... 

This contrasts sharply with the behavior of cyclopentanone and other alkanones for which the most important primary process from is intersystem crossing. 

Marongiu, B. Dernini, S. Polcaro, A. M. Thermodynamics of binary mixtures containing cyclic alkanones. Excess enthalpies of cyclopentanone and cyclohexanone + n-alkanes, + cyclohexane, + benzene, and + tetrachloromethane J. Chem. Eng. Data 1986, 31,185-189... 

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