A theoretical study of thermal [1, 3]-sigmatropic rearrangements of 3-trimethylsilyl-1-pyrazoline: Concerted vs. stepwise mechan

Abstract: Possible reaction mechanisms of 1,3-silyl and 1,3-hydrogen thermal rearrangements of trimethylsilyl-1pyrazoline and its model systems were theoretically explored using B3LYP, MP2, CR-CCSD(T), CASSCF(6,5), and MRMP2(6,5) theories. Nitrogen substitution at the center position of allylic moiety turned out to have a special stabilizing effect on diradical intermediates, allowing a stepwise pathway. This substitutional effect was attributed to the nitrogen lone pair electrons, which form strong -conjugations with diradicals. The second nitrogen substitution at the terminal allylic position selectively reduces the reaction barrier of antarafacial retention pathway, creating a compe

• Type: Journal
• Year: 2006
• Where: JCC
• Authors: Chultack Lim, Hee Soon Lee, Young-Woo Kwak, Cheol Ho Choi
• Keywords: JCC 2006, Nitrogen Lone Pair, Nitrogen Substitution, Possible Reaction Mechanisms