2577-90-4Relevant articles and documents
Propargyloxycarbonyl and propargyl groups for novel protection of amino, hydroxy, and carboxy functions
Kukase,Fukase,Kusumoto
, p. 1169 - 1170 (1999)
The propargyloxycarbonyl group readily introduced to both amino and hydroxy groups by using propargyl chloroformate is stable to neat TFA but is readily cleaved at ambient temperature by treatment with Co2(CO)8 and TFA in CH2Cl2 via formation of an alkyne-Co complex. The propargyl ester similarly serves as a good protecting group for carboxy functions.
Formation of lanthanide complexes with bipyridine-functionalized amide compounds and their unusually high amide reactivity
Araki,Kawaguchi,Kajikawa,Kaneko,Koshimizu
, p. 2729 - 2736 (1999)
The amide of 6-benzoylamino-6'-L-phenylalanyl-amino-2,2'-bipyridine (1a) was efficiently cleaved at 30°C to generate L-phenylalanine ester in methanol almost quantitatively. The reaction followed the Michaelis-Menten type via the 1:1 1a-Ln3+ complex. The half-life time of the scissile amide bond of the complex was as short as 2 min for the complex. The reactions depended on the structure of the substrates, which require 2,2'-bipyridine with two acylamino side chains at the 6,6'-positions and an amino group at the α-position of the scissile carbonyl. The less reactive 6-6'bis(benzoylamino)-2,2'-bipyridine with lanthanide cations formed 1:1 complexes. The formation constants were on the order of 103-105 cu dm/mole in methanol at 30°C. Coordination of the bipyridine nitrogens and the carbonyl oxygens was demonstrated in chloroform although coordination of the carbonyl oxygens was not seen in methanol.
Chiral N-hydroxybenzamides as potential catalysts for aerobic asymmetric oxidations
Capraro, Maria Grazia,Franchi, Paola,Lanzalunga, Osvaldo,Lapi, Andrea,Lucarini, Marco
, p. 6435 - 6443 (2014)
Chiral N-hydroxybenzamides (1H-3H) have been synthesized as precursors of chiral short-lived N-oxyl radicals 1?-3?. The latter species have been generated by oxidation of 1H-3H with Pb(OAc)4 or hydrogen abstraction from 1H-3H by the tert-butoxyl radical and characterized by UV-vis spectrophotometry and EPR spectroscopy. Through a kinetic study of the hydrogen atom transfer processes promoted by 1?-3? from three chiral benzylic substrates (1-phenylethylamine, 1-phenylethanol, and α-vinylbenzyl alcohol), a moderate chiral discrimination has been found, with selectivity factors 0.5 ≥ kH(S)/kH(R) ≥ 2.
Stereoretentive N-Arylation of Amino Acid Esters with Cyclohexanones Utilizing a Continuous-Flow System
Ichitsuka, Tomohiro,Komatsuzaki, Shingo,Masuda, Koichiro,Koumura, Nagatoshi,Sato, Kazuhiko,Kobayashi, Shū
supporting information, p. 10844 - 10848 (2021/05/31)
The N-arylation of chiral amino acid esters with minimal racemization is a challenging transformation because of the sensitivity of the α-stereocenter. A versatile synthetic method was developed to prepare N-arylated amino acid esters using cyclohexanones as aryl sources under continuous-flow conditions. The designed flow system, which consists of a coil reactor and a packed-bed reactor containing a Pd(OH)2/C catalyst, efficiently afforded the desired N-arylated amino acids without significant racemization, accompanied by only small amounts of easily removable co-products (i. e., H2O and alkanes). The efficiency and robustness of this method allowed for the continuous synthesis of the desired product in very high yield and enantiopurity with high space-time yield (74.1 g L?1 h?1) and turnover frequency (5.9 h?1) for at least 3 days.
Transition Metal-Free N-Arylation of Amino Acid Esters with Diaryliodonium Salts
Kervefors, Gabriella,Kersting, Leonard,Olofsson, Berit
supporting information, p. 5790 - 5795 (2021/03/08)
A transition metal-free approach for the N-arylation of amino acid derivatives has been developed. Key to this method is the use of unsymmetric diaryliodonium salts with anisyl ligands, which proved important to obtain high chemoselectivity and yields. The scope includes the transfer of both electron deficient, electron rich and sterically hindered aryl groups with a variety of different functional groups. Furthermore, a cyclic diaryliodonium salt was successfully employed in the arylation. The N-arylated products were obtained with retained enantiomeric excess.