838-13-1Relevant academic research and scientific papers
Enantioselective Diarylcarbene Insertion into Si-H Bonds Induced by Electronic Properties of the Carbenes
Evans, Declan,Houk, K. N.,Li, Mao-Lin,Li, Wen-Tao,Xu, Bin,Yang, Liang-Liang,Zhou, Qi-Lin,Zhu, Shou-Fei
supporting information, p. 12394 - 12399 (2020/08/06)
Catalytic enantioselection usually depends on differences in steric interactions between prochiral substrates and a chiral catalyst. We have discovered a carbene Si-H insertion in which the enantioselectivity depends primarily on the electronic characteristics of the carbene substrate, and the log(er) values are linearly related to Hammett parameters. A new class of chiral tetraphosphate dirhodium catalysts was developed; it shows excellent activity and enantioselectivity for the insertion of diarylcarbenes into the Si-H bond of silanes. Computational and mechanistic studies show how the electronic differences between the two aryls of the carbene lead to differences in energies of the diastereomeric transition states. This study provides a new strategy for asymmetric catalysis exploiting the electronic properties of the substrates.
Organic photochemical rearrangements of triplets and zwitterions; mechanistic and exploratory organic photochemistry
Zimmerman, Howard E.,Suryanarayan, Vijay
, p. 4091 - 4102 (2008/02/13)
There has been some controversy about the mechanisms of reactions of enones and dienones. The question has been whether a zwitterion or diradical is involved as the intermediate. In the case of ground state species it has not been recognized that zwitterions may have diradical character. In triplet reactions there is the question of whether the rearrangements take place at the initial T1 stage or subsequently as S0 ground state zwitterions or diradicals. We now have some new rearrangements bearing on these questions. In some cases it is the triplet which rearranges, while in others it is the SO zwitterion. The zwitterion vs. diradical nature of the S0 species has been assessed by both experimental as well as theoretical means. Similarly, both experiment and computational theory have been used to determine at what stage the triplet rearrangements occur and to determine the characteristics of the rearranging species. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
