738-79-4Relevant articles and documents
Redox Property of Enamines
Li, Yao,Wang, Dehong,Zhang, Long,Luo, Sanzhong
, p. 12071 - 12090 (2019/10/11)
Enamines are electron-rich compounds bearing intriguing redox properties. Herein, a series of secondary enamines condensed from primary amine and β-ketocarbonyls were synthesized and their electrochemical oxidation properties were systematically studied by cyclic voltammetry. Furthermore, theoretical calculation of oxidation potentials of enamines, particularly those catalytic intermediates, was also conducted to further broaden the scope investigated. Possible structural factors on oxidation and the nature of the resulted radical cation intermediates were revealed and discussed. Correlation of redox potentials with molecular properties such as highest occupied molecular orbital energies and natural population analysis charge were explored, and there appears no simple linear correlation. On the other hand, a good correlation with Mayr's nucleophilicity parameter N was noted among a range of catalytically relevant enamines. Spin population analysis disclosed that enamine radical cations mainly exhibit the carbon-center free radical feature. Taking experimental and computation data together, a comprehensive picture about the redox property of enamines is presented, which would provide guidance in the development of oxidative enamine catalysis and transformations.
Formation of dihydropyridone- and pyridone-based peptide analogs through aza-annulation of β-enamino ester and amide substrates with α-amido acrylate derivatives
Beholz, Lars G.,Benovsky, Petr,Ward, Donald L.,Barta, Nancy S.,Stille, John R.
, p. 1033 - 1042 (2007/10/03)
The aza-annulation of β-enamino ester and amide substrates with the mixed anhydride of 2-acetamidoacrylic acid was used for the efficient construction of highly substituted α-acetamido δ-lactam products. With the α-acetamido substituent, lactam functionality, and γ-carboxylate group, these δ-lactam products represent an interesting class of conformationally restricted dipeptide analogs. The framework of this lactam hub is structurally related to that of an α-amino acid coupled with a β-amino acid. When α-amino esters derived from naturally occurring amino acids were used in the enamine formation step, subsequent aza-annulation led to branched peptide surrogates with two C-termini that extended from a common N-terminus. Oxidation of the aza-annulation products resulted in the generation of a planar system with peptide functionality radiating from the 1, 3, and 5 positions of the pyridone hub. Alternatively, pyridone products could be formed directly from the enamino amides by reaction with 2-phenyl-4-(ethoxymethylene)oxazolone. Subsequent hydrolysis of the acetamido and ester substituents of the N-benzylpyridones was selectively performed to access unique β-amino acid products. Formation of the mixed anhydride of this acid, followed by amide bond formation with the ester of an α-amino acid, allowed extension of the peptide chain from the dihydropyridone structure.
