1666-77-9Relevant academic research and scientific papers
Reagent-dictated site selectivity in intermolecular aliphatic C-H functionalizations using nitrogen-centered radicals
Carestia, Anthony M.,Ravelli, Davide,Alexanian, Erik J.
, p. 5360 - 5365 (2018/06/27)
The site selectivities of intermolecular, aliphatic C-H bond functionalizations are central to the value of these transformations. While the scope of these reactions continues to expand, the site selectivities remain largely dictated by the inherent reactivity of the substrate C-H bonds. Herein, we introduce reagent-dictated site selectivity to intermolecular aliphatic C-H functionalizations using nitrogen-centered amidyl radicals. Simple modifications of the amide lead to high levels of site selectivity in intermolecular C-H functionalizations across a range of simple and complex substrates. DFT calculations demonstrate that the steric demand of the reacting nitrogen-centered radical is heavily affected by the substitution pattern of the starting amide. Optimization of transition state structures consistently indicated higher reagent-dictated steric selectivities using more hindered amides, consistent with experimental results.
The Regio- and Stereoselectivity of Radical Chlorination of Cycloalkanes with Different Halogen Carriers and Host-Guest Complexes
Schneider, Hans-Joerg,Philippi, Klaus
, p. 3056 - 3074 (2007/10/02)
The reaction of trans-1,4-dimethylcyclohexane (1) with (dichloroiodo)benzene (D), with most of the p-substituted D-derivatives, and with chlorine in carbon disulfide shows a regioselectivity of Rts ca. 10; reactions with o-substituted D-compounds or with D (R=H) in acetic acid or water show appreciable conversion, but lower selectivities of Rts ca. 5.Tertiary cyclohexyl radicals are chlorinated preferentially from the axial side with D (R=H); ortho-substituents in D, or replacement of CCl4 by CS2 or benzene lead to lower stereoselectivities.Chlorinations with iodophenyl derivatives, which are bound to a steroid matrix, exhibit no significant change in regioselectivity; the same is observed for reactions with chlorine in the presence of newly synthesized macrocyclic azacyclophane salts in water, although these form inclusion complexes with the hydrocarbons used and inhibit the hydrolysis of chlorides obtained from tetralin. α-Cyclodextrin, however, leads by selective complexation of 1 to selective chlorination of the primary C-H bonds.Syntheses and 13C NMR shifts of the azacyclophanes are described.
