83528-04-5Relevant articles and documents
BF3·Et2O as a metal-free catalyst for direct reductive amination of aldehydes with amines using formic acid as a reductant
Fan, Qing-Hua,Liu, Xintong,Luo, Zhenli,Pan, Yixiao,Xu, Lijin,Yang, Ji,Yao, Zhen,Zhang, Xin
supporting information, p. 5205 - 5211 (2021/07/29)
A versatile metal- and base-free direct reductive amination of aldehydes with amines using formic acid as a reductant under the catalysis of inexpensive BF3·Et2O has been developed. A wide range of primary and secondary amines and diversely substituted aldehydes are compatible with this transformation, allowing facile access to various secondary and tertiary amines in high yields with wide functional group tolerance. Moreover, the method is convenient for the late-stage functionalization of bioactive compounds and preparation of commercialized drug molecules and biologically relevant N-heterocycles. The procedure has the advantages of simple operation and workup and easy scale-up, and does not require dry conditions, an inert atmosphere or a water scavenger. Mechanistic studies reveal the involvement of imine activation by BF3and hydride transfer from formic acid.
Catalytic Transfer Hydrodebenzylation with Low Palladium Loading
Yakukhnov, Sergey A.,Ananikov, Valentine P.
supporting information, p. 4781 - 4789 (2019/09/16)
A highly-efficient catalytic system for hydrodebenzylation reaction is described. The cleavage of O-benzyl and N-benzyl protecting groups was performed using an uncommonly low palladium loading (0.02–0.3 mol%; TON up to 5000) in a relatively short reaction time. The approach was used for a variety of substrates including pharmaceutically important precursors, and gram-scale deprotection reaction was shown. Transfer conditions together with easy-to-make Pd/C catalyst are the key features of this debenzylation scheme. (Figure presented.).
Selective Rhodium-Catalyzed Reduction of Tertiary Amides in Amino Acid Esters and Peptides
Das, Shoubhik,Li, Yuehui,Bornschein, Christoph,Pisiewicz, Sabine,Kiersch, Konstanze,Michalik, Dirk,Gallou, Fabrice,Junge, Kathrin,Beller, Matthias
supporting information, p. 12389 - 12393 (2015/10/12)
Efficient reduction of the tertiary amide bond in amino acid derivatives and peptides is described. Functional group selectivity has been achieved by applying a commercially available rhodium precursor and bis(diphenylphosphino)propane (dppp) ligand together with phenyl silane as a reductant. This methodology allows for specific reductive derivatization of biologically interesting peptides and offers straightforward access to a variety of novel peptide derivatives for chemical biology studies and potential pharmaceutical applications. The catalytic system tolerates a variety of functional groups including secondary amides, ester, nitrile, thiomethyl, and hydroxy groups. This convenient hydrosilylation reaction proceeds at ambient conditions and is operationally safe because no air-sensitive reagents or highly reactive metal hydrides are needed.
Synthesis of syn-γ-amino-β-hydroxyphosphonates by reduction of β-ketophosphonates derived from L-proline and L-serine
Ordonez, Mario,Lagunas-Rivera, Selene,Hernandez-Nunez, Emanuel,Labastida-Galvan, Victoria
scheme or table, p. 1291 - 1301 (2010/06/13)
The reduction of γ-N-benzylamino-β-ketophosphonates 6 and 10, readily available from L-proline and L-serine, respectively, can be carried out in high diastereoselectivity with catecholborane (CB) in THF at -78 °C to produce the syn-γ-N-benzylamino-β-hydro
The First Enantioselectice Total Syntheses of the Allopumiliotoxin A Alkaloids 267A and 339B
Goldstein, Steven W.,Overmann, Larry E.,Rabinowitz, Michael H.
, p. 1179 - 1190 (2007/10/02)
Short, highly stereocontrolled, asymmetric total syntheses of the title amphibian alkaloids are described.In the first stage the indolizidine ketone 11 is assembled from L-proline in enantiomerically pure form.This short sequence proceeds in five laborato
Asymmetric Synthesis of Threonine and Partial Resolution and Retroracemization of α-Amino Acids via Copper(II) Complexes of Their Schiff Bases with (S)-2-N-(N'-Benzylprolyl)aminobenzaldehyde and (S)-2-N-(N'-Benzylprolyl)aminoacetophenone. Crystal and Molecular Structure of a ...
Belokon', Yu. N.,Zel'tzer, I. E.,Bakhmutov, V. I.,Saporovskaya, M. B.,Ryzhov, M. G.,et al.
, p. 2010 - 2017 (2007/10/02)
The work described here is concerned with the search for universal chiral reagent for the asymmetric synthesis, resolution, and retroracemization of amino acids.Reaction of N-benzyl-(S)-proline with o-aminobenzaldehyde or o-aminoacetophenone has given (S)-2-N-(N'-benzylprolyl)aminobenzaldehyde ((S)-BPAB) or (S)-2-N-(N'-benzylprolyl)aminoacetophenone ((S)-BPAAPh).These chiral reagents have interacted with α-amino acids (aa) and Cu(II) ions to form complexes CuII and CuII in which Schiff bases (S)-BPAB-aa or (S)-BPAAPh-aa act as tetradentate ligands and coordinate the copper ion by the nitrogen atoms of the pyrrolidine fragment, the deprotonated amide group, and the amino acid fragment and by the oxygen atom of the carboxylate.Such a structure was supported by data on elemental analysis, the molecular weight measurements, and electron, IR, and CD spectra.It was finally confirmed by an X-ray diffraction analysis of CuII.One equivalent of (S)-BPAB has reacted with 2 equiv of (R,S)-aa and 2 equiv of Cu(II), having given preferential formation of copper complexes of Schiff bases with (S)-aa.After their extraction with chloroform the amino acid enriched with the R enantiomer remained in the aqueous solution.In this manner partial resolution of racemic amino acids (Ala, Nva, Phe, Val, Thr) has been carried out with enantiomeric purity 4-50percent. (S)-BPAB or (S)-BPAAPh treatment of a racemic amino acid in the presence of Cu(II) ions (reagents ratio 1:1:1) and CH3O- ions permits enantiomeric enrichment via conversion of the R into S enantiomer (retroracemization).Thus (S)-Ala, (S)-Nva, (S)-Leu, (S)-Val, (S)Phe, and (S)-PhGly of enantiomeric purity 36, 12, 22, 54, 42, and 35percent, respectively, were obtained from racemic samples.CH3O--catalyzed reaction of CuII or CuII with acetaldehyde has given rise to a mixture of diastereomeric complexes, which upon removal of Cu(II) by H2S gave (R)-threonine of 60percent or 97-100percent enantiomeric purity and the threo/allo ratio 6:1 or 19:1, respectively, and permitted recovery of an unchanged initial chiral reagent (S)-BPAB or (S)-BPAAPh.
