3856-83-5Relevant academic research and scientific papers
Nucleophilic Substitution and Competing Elimination in Cyclohexane and Steroid Reactions. A Comparison of Experiments and Force Field Calculations including the Regioselectivity of Steroid Eliminations
Gschwendtner, W.,Hoppen, V.,Schneider, H.-J.
, p. 1201 - 1226 (2007/10/02)
A number of nucleophilic replacements including hydroxyl group substitutions are reported which show clean inversion with 3β-substituted cholestanes, whereas comparable cyclohexanes yield largely olefinic byproducts.Model calculations with the MM1 molecular mechanics force field demonstrate that twist boot intermediates as proposed in the literature for cyclohexane eliminations will require significantly higher strain energy in the steroid only if the interaction of both leaving group and attacking agent at Cβ-H is included.The predominance of Δ2 over Δ3 products in the steroid eliminations is based less on steric energy differences of these olefins, than on those of the preceding transition states.For the steroid all-chair ground state MM1, MM2 and crystal structure results are found to be in agreement.The calculations show the absence of conformational transmission of the A-ring twist-boat distortions in the C and D rings.
