Seven‐membered lactones undergo selective SmI2–H2O‐promoted radical cyclization to form substituted cyclooctanols. The products arise from an exo‐mode of cyclization rather than the usual endo‐attack employed in the few radical syntheses of cyclooctanes. The process is terminated by the quenching of a chiral benzylic samarium. A labeling experiment and neutron diffraction study have been used for the first time to probe the configuration and highly diastereoselective deuteration of a chiral organosamarium intermediate.

Seven-membered lactones undergo selective SmI 2 -H 2 O-promoted radical cyclization to form substituted cyclooctanols.T he products arise from an exo-mode of cyclization rather than the usual endo-attacke mployed in the few radical syntheses of cyclooctanes.T he process is terminated by the quenching of ac hiral benzylic samarium. Al abeling experiment and neutron diffraction study have been used for the first time to probe the configuration and highly diastereoselective deuteration of ac hiral organosamarium intermediate.

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