Stereoselectivity of the Transfer of Hydrogen Atoms to Cyclic Alkyl Radicals

Abstract

AbstractThe addition of cyclohexane to alkylmaleic anhydrides 1a‐f via cyclic radicals 2a‐f gave a mixture of (Z)‐ and (E)‐2,3‐dialkylsuccinic anhydrides 3a‐f. The stereoselectivity of the hydrogen transfer from cyclohexane to radicals 2a‐d was measured in the temperature range of 200‐260°C, and the relative activation parameters of the formation of (Z)‐ and (E)‐3 were determined. The stereoselectivity of the hydrogen transfer from cyclohexylmercuric hydride at 25°C was measured as well. The results are rationalized assuming steric interactions in the transition state of H donor and β substituent and of α and β substituent, respectively. An X‐ray structure analysis of the highly strained addition product (Z)‐3d was performed.