Onset on Anh Hyperconjugation in the Transition State of Carbonyl Addition by Deactivation of Periplanar Vicinal Bonds

Face Selection in Addition and Elimination in Sterically Unbiased Systems

“…In pursuit of that notion, we studied the reaction of lithium borohydride dissolved in ether with 7-monohydrylperfluoroadamantan-2-one (Scheme ), in which fluorine substitution abrogates the ability of the vicinal bonds to function as donors, and converts them into acceptors instead. As the scheme indicates, this ketone does indeed follow the prediction made on the basis of reverse electron flow 5 …”

Inductive and Resonance Effects of Substituents on π-Face Selection

“…The anti preference in NaBH 4 reduction of 5- H -perfluoroadamantan-2-one was proposed to result from the Anh-type stabilization . Indeed, the C−C bonds are expected to be incapable of hyperconjugation in the perfluorinated compound.…”

Electronic Control of Facial Selection in Additions to Sterically Unbiased Ketones and Olefins

“…In many of the examples cited in the previous section, the reasons for the failure of the Cieplak model of diastereoselection can be readily recognized. In the polyfluoroderivative, 26 , the Felkin−Anh hyperconjugative model evidently comes into play because of low-lying C−F σ* orbitals on the substrate . In the substituted cyclohexadienones, 29 , spiro derivatives, 30 , and the dibenzobicyclo-[2.2.2]octanones, 21 , the scope of differential hyperconjugative interactions induced by the remote substituent is significantly curtailed by the intervening π units.…”