10.1016/j.tet.2008.03.027
The study presents an investigation into the selective synthesis of functionalized cycloheptadienes through tandem enyne metathesis, utilizing Grubbs' catalyst to achieve regio- and site-selective ring expansion of dienes and substituted cyclopentenes. The research focuses on the influence of ring strain on the reactivity and selectivity of the metathesis process, elucidating the mechanistic aspects that contribute to the formation of 1,3-cycloheptadienes. The study also explores the reaction's scope and limitations, including the impact of different substituents and the potential for further functionalization of the synthesized cycloheptadienes. The findings provide valuable insights into the control of alkene stereoselectivity in enyne metathesis and the development of efficient synthetic strategies for complex molecule synthesis.
10.1021/ja00221a093
The research investigates the Cope rearrangement and the selective reduction of acyclic ketones via electron-transfer-initiated processes. In the study of the Cope rearrangement, the chair and boat transition states were analyzed using CASSCF calculations. The chair transition state was found to have an energy of 40.7 kcal/mol above the CAS-optimized C2 geometry for 1,5-hexadiene, with an enthalpy of activation of 37.7 kcal/mol after correction for vibrational energy differences. The boat transition state had a higher energy and a larger value of R (2.316 ?) compared to the chair. The study found that both transition states are concerted and synchronous, contrasting with previous findings from AM1 and ab initio calculations. In the study of the selective reduction of acyclic ketones, various reducing agents were used, including LiAlH4, L-Selectride, Li-NH3, Li-NH3-NH4+, Na-EtOH, and SmI2. The results showed that reductions via electron-transfer-initiated processes, such as Birch reduction, Bouvault-Blanc reduction, and samarium iodide reduction, predominantly produced the anti-Cram isomer, while LiAlH4 and L-Selectride reductions produced the Cram isomer. The preference for the anti-Cram isomer in electron-transfer-initiated reductions is attributed to the relative stability of carbanion intermediates and the protonation step.