36873-36-6Relevant academic research and scientific papers
Asymmetric Reductive Carbocyclization Using Engineered Ene Reductases
Heckenbichler, Kathrin,Schweiger, Anna,Brandner, Lea Alexandra,Binter, Alexandra,Toplak, Marina,Macheroux, Peter,Gruber, Karl,Breinbauer, Rolf
supporting information, p. 7240 - 7244 (2018/06/15)
Ene reductases from the Old Yellow Enzyme (OYE) family reduce the C=C double bond in α,β-unsaturated compounds bearing an electron-withdrawing group, for example, a carbonyl group. This asymmetric reduction has been exploited for biocatalysis. Going beyond its canonical function, we show that members of this enzyme family can also catalyze the formation of C?C bonds. α,β-Unsaturated aldehydes and ketones containing an additional electrophilic group undergo reductive cyclization. Mechanistically, the two-electron-reduced enzyme cofactor FMN delivers a hydride to generate an enolate intermediate, which reacts with the internal electrophile. Single-site replacement of a crucial Tyr residue with a non-protic Phe or Trp favored the cyclization over the natural reduction reaction. The new transformation enabled the enantioselective synthesis of chiral cyclopropanes in up to >99 % ee.
Mechanistic investigation of oxidative Mannich reaction with tert-butyl hydroperoxide. the role of transition metal salt
Ratnikov, Maxim O.,Doyle, Michael P.
supporting information, p. 1549 - 1557 (2013/03/14)
A general mechanism is proposed for transition metal-catalyzed oxidative Mannich reactions of N,N-dialkylanilines with tert-butyl hydroperoxide (TBHP) as the oxidant. The mechanism consists of a rate-determining single electron transfer (SET) that is uniform from 4-methoxy- to 4-cyano-N,N-dimethylanilines. The tert-butylperoxy radical is the major oxidant in the rate-determining SET step that is followed by competing backward SET and irreversible heterolytic cleavage of the carbon-hydrogen bond at the α-position to nitrogen. A second SET completes the conversion of N,N-dimethylaniline to an iminium ion that is subsequently trapped by the nucleophilic solvent or the oxidant prior to formation of the Mannich adduct. The general role of Rh2(cap) 4, RuCl2(PPh3)3, CuBr, FeCl 3, and Co(OAc)2 in N,N-dialkylaniline oxidations by T-HYDRO is to initiate the conversion of TBHP to tert-butylperoxy radicals. A second pathway, involving O2 as the oxidant, exists for copper, iron, and cobalt salts. Results from linear free-energy relationship (LFER) analyses, kinetic and product isotope effects (KIE and PIE), and radical trap experiments of N,N-dimethylaniline oxidation by T-HYDRO in the presence of transition metal catalysts are discussed. Kinetic studies of the oxidative Mannich reaction in methanol and toluene are also reported.
A biologically inspired CuI/topaquinone-like co-catalytic system for the highly atom-economical aerobic oxidation of primary amines to imines
Largeron, Martine,Fleury, Maurice-Bernard
body text, p. 5409 - 5412 (2012/06/18)
Acting together: Low catalytic amounts of CuI and topaquinone-like catalyst 1ox (see scheme) are sufficient to activate the α-C-H bond of primary amines, which are converted into alkylated imines under ambient conditions. This atom-economical process tolerates the presence of various reactive functional groups and allows selective cross-coupling of two amines. Copyright
Oxidation of unactivated primary aliphatic amines catalyzed by an electrogenerated 3,4-azaquinone species: A small-molecule mimic of amine oxidases
Largeron, Martine,Neudorffer, Anne,Fleury, Maurice-Bernard
, p. 1026 - 1029 (2007/10/03)
High catalytic performance of the electrogenerated amine oxidase mimic 3,4-iminoquinone 1ox is observed under metal-free conditions in the chemoselective oxidation reaction of unactivated primary aliphatic amines.
