63649-24-1Relevant academic research and scientific papers
A Model Study of Intramolecular Asymmetric Radical Cyclizations of a-Ester and α-Amide Radicals
Yeh, Ru-Long,Jiaang, Weir-Torn,Tsai, Yeun-Min
, p. 253 - 260 (2007/10/03)
Starting from malonate, a practical route was developed for the synthesis of α-phenylthio acid 3. Several chiral compounds including (-)-menthol, (-)-8-phenylmenthol and a camphor based oxazolidinone 8 reacted with 3 to give α-phenylthio esters or amide. These sulfides cyclized efficiently when reacted with tributyltin hydride. Among the chiral auxiliaries used, 8-phenylmenthyl group displayed moderate asymmetric induction (64% ee for cis-product and 40% ee for trans-product). Based on this results, a transition state model was proposed to explain the observed stereoselectivity. In this model, due to π,π-orbital overlap of the phenyl ring and the carbonyl, the si-face of the most stable conformer of the radical was shielded. This controlled the carbon-carbon bond formation to occur from the re-face.
The Influence of Intramolecular Dynamics on Branching Ratios in Thermal Rearrangements
Newmann-Evans, Richard H.,Simon, Reyna J.,Carpenter, B. K.
, p. 695 - 711 (2007/10/02)
1- and 2-phenylbicyclohex-2-enes-5-d undergo thermal rearrangement to give products, differing only in the location of the deuterium, in ratio of about 9:1, but with identical activation enthalphies.Similarly, opticallly active trans-2-methyl-1-(trans-2-phenylethenyl)cyclopropane is found to rearrange to enantiomeric methylphenylcyclopentenes that are formed in a 5.9:1 ratio but with virtually identicyl activation enthalphies.Barring repeated coincidence, these results do not seem to be explicable within the framework of statistical theories of unimolecular kinetics such as RRKM theory, transition state theory, and variational transition state theory.The possible influence of dynamic effects in these and other unimolecular reactions is discussed.
