Cyclohexyl radicals, stereochemistry

This result shows than the initially added trichloromethyl group has little influence on the stereochemistry of the subsequent bromine atom-abstraction. The intermediate 2-(trichlor-omethyl)cyclohexyl radical presumably relaxes to the equatorial conformation faster than bromine-atom abstraction occurs. In contrast with addition to A -octahydronaphthalene, the addition is exclusively /ran -diaxial ... 

Cyclobutane and Heterocyclic Analogs, Stereochemistry of (Moriarty) Cyclohexyl Radicals, and Vinylic, The Stereochemistry of (Simamura)... 

Cyclic molecules also permit deductions about stereochemistry without the necessity for optically active compounds, and the stereochemistry of a number of reactions of 4-substituted cyclohexyl radicals has been investigated. These reactions give mixtures of cis and trans isomers, indicating that the radical intermediates in these reactions do not retain the stereochemistry of the radical precursor. Such reactions are not usually very stereoselective, but some show a preference for... 

Radicals, Cyclohexyl and Vinylic, The Stereochemistry of Simamura) Reduction, of Cyclic and Bicyclic Ketones by Complex Metal Hydrides... 

In germanium chemistry the importance of free radical pathways in substitution reactions of secondary bromides with R3GeLi (R = CH3, CgHs) reagents is strongly indicated by product stereochemistry in cyclohexyl systems and by cyclization of the cA-heptene-2-yl moiety to yield [(2-methylcyclopentenyl)methyl]germanes, with the appropriate cis/trans ratio, as shown in equation 180, Table 9 and equations 181 and 182189. 

Naito has also described analogous tandem radical addition-cyclization processes under iodine atom-transfer reaction conditions [16,32], Treatment of 186 with z-PrI (30 eq.) and triethylborane (3x3 eq.) in toluene at 100 °C gave, after cleavage from the resin, the desired lactam product 190 in 69% yield (Scheme 46). Similar reactions involving cyclohexyl iodide, cyclopentyl iodide, and butyl iodide were also reported as well as the reaction with ethyl radical from triethylborane [16,32], The relative stereochemistry of the products was not discussed. 

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