Synthesis of enaminones
Simple and direct nucleophilic addition of secondary amines to 1,2,3-triazine under mild reaction conditions cleanly provides β-aminoenals in good yields. The reaction proceeds by amine nucleophilic addition to C4 of the 1,2,3-triazine, in situ loss of N2, and subsequent imine hydrolysis.
R. E. Quiñones, C. M. Glinkerman, K. Zhu, D. L. Boger, Org. Lett., 2017, 19, 3568-3571.
Bench-stable sodium 3-oxo-enolates can be reacted with amines in the presence of an acid and a desiccant to provide β-amino-α,β-unsaturated carbonyl compounds.
R. S. Reyno, A. Sugunan, S. Ranganayakulu, C. H. Suresh, G. Rajendar, Org. Lett., 2020, 22, 1040-1045.
Ceric ammonium nitrate catalyzes the reaction between aromatic or aliphatic primary amines and a variety of β-dicarbonyl compounds, including β-ketoesters, β-ketothioesters and β-diketones to give β-enaminones in good to excellent yields at room temperature in short reaction times.
V. Sridharan, C. Avendaño, J. Carlos Menéndez, Synlett, 2007, 2133-2142.
Mechanochemical grinding in the presence of KHSO4 and SiO2 enables a facile amination of solid 1,3-dicarbonyl compounds with ammonium salts or amines in solid state to yield the corresponding β-imino derivatives in high yields. The method has the advantage of simple manipulation and mild conditions.
S.-L. Xu, C.-P. Li, J.-H. Li, Synlett, 2009, 818-822.
The coupling of acid chlorides with terminal alkynes using one equivalent of triethylamine under Sonogashira conditions followed by subsequent addition of amines or amidinium salts to the intermediate alkynones allows a straightforward access to enaminones and pyrimidines under mild conditions and in excellent yields.
A. S. Karpov, T. J. J. Müller, Synthesis, 2003, 2815-2826.
A BF3·OEt2-catalyzed cyclization of 1-iodoalkyne and α-keto acid followed by an amine-mediated ring-opening enable a metal-free direct synthesis of β-ketoenamines in one pot. The reaction tolerates transition metal-sensitive functional groups.
X. Zeng, C. Liu, W. Yang, Y. Weng, X. Wang, Y. Hu, J. Org. Chem., 2019, 84, 3656-3661.
The trisulfur radical anion triggers a C(sp2)-H amination of α,β-unsaturated carbonyl derivatives with simple amines to provide a variety of synthetically valuable N-unprotected and secondary β-enaminones with absolute Z selectivity and tertiary β-enaminones with E selectivity.
K. X. Nguyen, P. H. Pham, T. T. Nguyen, C.-H. Yang, H. T. B. Pham, T. T. Nguyen, H. Wang, N. T. S. Phan, Org. Lett., 2020, 22, 9751-9756.
A Au(I)-catalyzed tandem amide addition and Meyer-Schuster rearrangement enables the synthesis of enamides from primary amides and propargyl aldehydes. Enamide stereochemistry was controlled simply by changing solvents and adding a catalytic amount of acid.
S. M. Kim, D. Lee, S. Hyeok Hong, Org. Lett., 2014, 16, 6168-6171.
A copper-catalyzed four-component formal oxyaminalization of alkenes with Togni's reagent and amines in the presence of molecular oxygen as both the oxidant and oxygen source efficiently provides a range of structurally diverse α-oxoketene aminals. This simple procedure offers excellent functional group tolerance, broad substrate scope, and mild conditions.
L. Wang, C. Qi, T. Guo, H. Jiang, Org. Lett., 2019, 21, 2223-2226.