79893-94-0Relevant academic research and scientific papers
Regiodivergent Enantioselective γ-Additions of Oxazolones to 2,3-Butadienoates Catalyzed by Phosphines: Synthesis of α,α-Disubstituted α-Amino Acids and N,O-Acetal Derivatives
Wang, Tianli,Yu, Zhaoyuan,Hoon, Ding Long,Phee, Claire Yan,Lan, Yu,Lu, Yixin
, p. 265 - 271 (2016/01/25)
Phosphine-catalyzed regiodivergent enantioselective C-2- and C-4-selective γ-additions of oxazolones to 2,3-butadienoates have been developed. The C-4-selective γ-addition of oxazolones occurred in a highly enantioselective manner when 2-aryl-4-alkyloxazol-5-(4H)-ones were employed as pronucleophiles. With the employment of 2-alkyl-4-aryloxazol-5-(4H)-ones as the donor, C-2-selective γ-addition of oxazolones took place in a highly enantioselective manner. The C-4-selective adducts provided rapid access to optically enriched α,α-disubstituted α-amino acid derivatives, and the C-2-selective products led to facile synthesis of chiral N,O-acetals and γ-lactols. Theoretical studies via DFT calculations suggested that the origin of the observed regioselectivity was due to the distortion energy that resulted from the interaction between the nucleophilic oxazolide and the electrophilic phosphonium intermediate.
The Role of the Amino Protecting Group during Parahydrogenation of Protected Dehydroamino Acids
Cerutti, Erika,Viale, Alessandra,Nervi, Carlo,Gobetto, Roberto,Aime, Silvio
, p. 11271 - 11279 (2015/12/01)
A series of dehydroamino acids endowed with different protective groups at the amino and carboxylate moieties and with different substituents at the double bond have been reacted with parahydrogen. The observed ParaHydrogen Induced Polarization (PHIP) effects in the 1H NMR spectra are strongly dependent on the amino protecting group. DFT calculations allowed us to establish a relationship between the structures of the reaction intermediates (whose energies depend on the amido substitution) and the observed PHIP patterns.
ASYMMETRISCHE KATALYSEN. XXX. ENANTIOSELEKTIVE HYDRIERUNG VON CROTONSAEUREDERIVATEN MIT RHODIUM-PHOSPHIN-KATALYSATOREN
Brunner, Henri,Knott, Alfons,Kunz, Manfred,Thalhammer, Elisabeth
, p. 55 - 62 (2007/10/02)
The Z- and E-isomers of the α-N-benzoylamino-2-butenoic acid methyl ester, the E/Z mixtures of α-N-benzoylamino-2-butenoic acid, and the Z-form of α-N-acetylamino-2-butenoic acid were hydrogenated enantioselectively.The hydrogenation products are derivatives of α-aminobutyric acid, which can be reduced to aminobutanol, the optically active component of the antituberculosis drug (+)-ethambutol.In situ catalysts consisting of 2 and the optically active phosphine ligands (+)- and (-)-Norphos, (+)-Prophos, (-)-Chiraphos, (-)-BPPFA, (-)-Diop, and (+)- and (-)-CpMn(CO)2diop were used.The best results were obtained with the substrate (Z)-α-acetylamino-2-butenoic acid and the catalyst 2/(-)-Norphos with 91.5percent e.e.
Von der basenkatalysierten Ringoeffnung von 2H-Azirinen zu einer α-Alkylierungsmethode von primaeren Aminen
Schulthess, Adrian Heinz,Hansen, Hans-Juergen
, p. 1322 - 1336 (2007/10/02)
It is shown than fluorene-9'-spiro-2-(3-phenyl-2H-azirine) (1) on treatment with various alcohols in the presence of the corresponding alkoxide ions yields N-(9'-fluorenyl)benzimidates 2a-d (Scheme 1). 2,2,3-Triphenyl-2H-aziridine (3) reacts with methanol in a similar manner (Scheme 2).Benzimidates 2a (Scheme 3), 8 (Scheme 4) and 10 (Scheme 5) can easily be deprotonated by butyllithium (BuLi) or lithium diisopropylamide (LDA) in tetrahydrofuran (THF) to 1-methoxy-2-aza-allylanions, that can be alkylated, at C(3), exclusively, by various electrophiles (e.g.R-X (X = I, Br), RCHO or methyl acrylate (see also Scheme 6)).As the acidic hydrolyses (1 N HCl) of benzimidates 9 and 11 leads to the corresponding α-alkylated free amines 15 and 18 (Scheme 7 and 8), benzoyl derivatives 16 and 19 are obtained from the hydrolysis under basic conditions.On the other hand it is observed that a catalyzed Chapman rearrangement of 9 and 11 results in the formation of N-benzoyl-N-methyl derivatives 17 and 20 (Scheme 7 and 8).The described reactions offer a simple method for the α-alkylation of actived primary amines.
