- Development of Br?nsted Base-Photocatalyst Hybrid Systems for Highly Efficient C-C Bond Formation Reactions of Malonates with Styrenes
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Br?nsted base-photocatalyst hybrid systems have been developed for reactions of malonates with styrene derivatives. The concept of this process lies in the photo-oxidation of catalytic amounts of the enolate to form reactive radicals that react with alken
- Ba?, Sebastian,Kobayashi, Shū,Yamashita, Yasuhiro
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p. 10546 - 10550
(2020/11/09)
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- Non- C2-Symmetric Chiral-at-Ruthenium Catalyst for Highly Efficient Enantioselective Intramolecular C(sp3)-H Amidation
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A new class of chiral ruthenium catalysts is introduced in which ruthenium is cyclometalated by two 7-methyl-1,7-phenanthrolinium heterocycles, resulting in chelating pyridylidene remote N-heterocyclic carbene ligands (rNHCs). The overall chirality results from a stereogenic metal center featuring either a or Δabsolute configuration. This work features the importance of the relative metal-centered stereochemistry. Only the non-C2-symmetric chiral-at-ruthenium complexes display unprecedented catalytic activity for the intramolecular C(sp3)-H amidation of 1,4,2-dioxazol-5-ones to provide chiral -lactams with up to 99:1 er and catalyst loadings down to 0.005 mol % (up to 11 ?200 TON), while the C2-symmetric diastereomer favors an undesired Curtius-type rearrangement. DFT calculations elucidate the origins of the superior C-H amidation reactivity displayed by the non-C2-symmetric catalysts compared to related C2-symmetric counterparts.
- Zhou, Zijun,Chen, Shuming,Hong, Yubiao,Winterling, Erik,Tan, Yuqi,Hemming, Marcel,Harms, Klaus,Houk,Meggers, Eric
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supporting information
p. 19048 - 19057
(2019/12/04)
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- Selective photochemical monoalkylation of active methylene compounds by alkenes. A green pathway for carbon-carbon bond formation
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A novel photochemical method for selective α-monoalkylation of active methylene compounds has been developed. Aryl substituted alkenes and an aliphatic diene can be used as alkyl sources for these reactions, which proceed via polycyanoarene sensitized, photoinduced electron transfer pathways that are promoted using very mild conditions (ambient temperature, without noble metals and halogens, and with weak bases such as alkali metal carbonate). The reactions that comprise the new synthetic methods developed in this effort are both safe and environmentally friendly. Especially noteworthy is the fact that photochemical alkylation reactions of β-ketoesters (e.g., acetoacetic and malonic esters) can be used in the place of conventional strong base promoted processes.
- Ohashi, Maki,Nakatani, Keisuke,Maeda, Hajime,Mizuno, Kazuhiko
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experimental part
p. 161 - 170
(2010/12/18)
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