The Stereochemistry of the Addition of Hydrogen Bromide to 1,2-Dimethylcyclohexene

Electrophilic Addition to Alkenes: The Relation between Reactivity and Enthalpy of Hydrogenation: Regioselectivity is Determined by the Stability of the Two Conceivable Products

“…Addition of HBr to 1,2‐dimethylcyclohexene in pentane at 0 °C gave exclusively the anti ‐addition product. In acetic acid at 25 °C, the anti ‐addition product was also obtained exclusively at short reaction times, with some rearrangements of the initial product occurring at very long reaction times 20…”

The Isolation and Structural Elucidation of Euparotin Acetate, a Novel Guaianolide Tumor Inhibitor from Eupatorium rotundifolium

“…4 The intermediate leading to the product-determining step might be either a classical carbonium ion pair5 or a complex.6,7 It has also been suggested that the reaction might proceed in some cases via a concerted irons attack by both the electrophile and the nucleophile on the double bond. 7 The last two possibilities cannot be important in the present cases because the products are almost exclusively tertiary exo chlorides. The result with a-fenchene is of particular interest since it has been argued that…”

“…The carbon and oxygen atoms were located in three-dimensional electron-density distributions for which the Fourier coefficients were weighted according to the method proposed by Sim. 7 The atomic coordinates were subsequently refined by the least-squares method and the present value of R is 13.1%. The bromine atom was assigned anisotropic temperature factors, but the carbon and oxygen atoms were assigned only isotropic values.…”

The Hydrochlorination of 2-Methylenenorbornane and Related Derivatives. Evidence for the Absence of a Symmetrical Nonclassical Intermediate in the Hydrochlorination of 1-Methyl-d3-2-methylenenorbornane

“…4 The intermediate leading to the product-determining step might be either a classical carbonium ion pair5 or a complex.6,7 It has also been suggested that the reaction might proceed in some cases via a concerted irons attack by both the electrophile and the nucleophile on the double bond. 7 The last two possibilities cannot be important in the present cases because the products are almost exclusively tertiary exo chlorides. The result with a-fenchene is of particular interest since it has been argued that the presence of the 7,7-dimethyl substituents should, for steric reasons, result in the formation of endo product, except in cases where nonclassical bridging directs the entering nucleophile to the exo position.8•9 If this argument is valid, the formation of the 2,7,7-trimethylexo-norbornyl chloride in the hydrochlorination of afenchene would appear to require the formation of a bridged cation.…”