Guindon, Yvan Faucher, Anne-Marie Bourque, Élyse Caron, Valérie Jung, Grace Landry, Serge R. The Exocyclic Effect:  Protecting Group Strategy to Enhance Stereoselectivity in Hydrogen Transfer Reactions of Acyclic Free Radicals To enhance the diastereoselectivity of the hydrogen transfer reaction of acyclic substrates bearing 1,2- or 1,3-diols, the feasibility of a strategy employing bifunctional protecting groups has been demonstrated. This strategy is based upon the “exocyclic effect” or the significant improvement of <i>anti</i>-selectivity exhibited by the reductions of substrates in which the two substituents (R<sub>1</sub> and Y) at the stereogenic center α to the radical center are linked together. A rationale for the excellent facial discrimination of these <i>exocyclic</i> radicals is offered based on an analysis of transition state models, which considers both steric and electronic factors. acyclic substrates;stereogenic center α;diastereoselectivity;Exocyclic;Strategy;feasibility;hydrogen transfer reaction;steric;R 1;strategy;discrimination;diol;Acyclic Free Radicals;factor;substituent;rationale;bifunctional;Hydrogen Transfer Reactions;Enhance Stereoselectivity;exocyclic radicals;analysis;Protecting;transition state models 1997-12-26
    https://acs.figshare.com/articles/journal_contribution/The_Exocyclic_Effect_Protecting_Group_Strategy_to_Enhance_Stereoselectivity_in_Hydrogen_Transfer_Reactions_of_Acyclic_Free_Radicals/3708183
10.1021/jo971595s.s001