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Synthesis of enamines and related structures

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Synthesis of      
Enaminones β-Enamino Esters
α-Ketoenamines Ketene Aminals


Literature


By employing Pd(OAc)2 and (t-Bu)2PNP(i-BuNCH2CH2)3N as ligand, a broad range of aryl bromides and chlorides possessing base-sensitive substituents provide coupling products with bulky aryl amines in good to excellent yields. An efficient coupling of vinyl bromides with a variety of amines produces imines and enamines at room temperature.
Ch. V. Reddy, J. V. Kingston, J. G. Verkade, J. Org. Chem., 2008, 73, 3047-3062.


CuF2/DMAP is as an excellent catalytic system for vinylsilane-promoted N-vinylation of amides and azoles at room temperature without an external fluoride source. Valuable monomers for water-soluble polymers, viz., NVP, NVC, and NVIBA, were synthesized on a gram scale.
K. Mondal, S. Patra, P. Halder, N. Mukhopadhyay, P. Das, Org. Lett., 2023, 25, 1235-1240.


Michael adducts are provided by a reaction of alkylidene malonates with enamines, which are generated from vinyl bromides and pyrrolidine by a prior palladium-catalysed C-N bond formation.
M. C. Willis, J. Chauhan, W. G. Whittinham, Org. Biomol. Chem., 2005, 3, 3094-3095.


A NiH-catalyzed strategy for the hydroamidation of alkynes with dioxazolones allows convenient access to synthetically useful secondary enamides in (E)-anti-Markovnikov or Markovnikov selectivity. The reaction is viable for both terminal and internal alkynes and also tolerates a range of functional groups. The presence of H2O is crucial for high catalyst turnovers.
X. Lyu, J. Zhang, D. Kim, S. Seo, S. Chang, J. Am. Chem. Soc., 2021, 143, 5867-5877.


Hydrozirconation of an alkyne with the Schwartz reagent forms a vinyl zirconium intermediate, which directly undergoes a copper-catalyzed electrophilic enamidation with dioxazolones. High functional group tolerance of hydrozirconation enables the use of functionalized alkynes including esters.
S. Banjo, K. Nakata, E. Nakasuji, S. Yasui, N. Chida, T. Sato, Org. Lett., 2022, 24, 8662-8666.


A metal-free regio- and stereoselective intermolecular hydroamination of arylacetylenes with aliphatic secondary amines provides various (E)-enamines in the presence of ethylene glycol as a solvent. The solvent plays a major role through hydrogen bonding and proton exchange.
J. Bahri, N. Tanbouza, T. Ollevier, M. Taillefer, F. Monnier, Synthesis, 2019, 51, 2086-2090.


A range of enol triflates can be coupled with amides, carbamates, and sulfonamides using palladium catalysis. This method allows the synthesis of enamides, which may not be readily available by other means.
D. J. Wallace, D. J. Klauber, C.-Y. Chen, R. P. Volante, Org. Lett., 2003, 5, 4749-4752.


A hydroamination of unactivated alkynes with lithium bis(fluorosulfonyl)imide (LiN(SO2F)2) provides a single regioisomer of a sulfonyl fluorides in very good yields under mild conditions. This method offers broad functional group compatibility and delivers the target vinyl fluorosulfonimides even in gram-scale. Vinyl fluorosulfonimides can be used for the synthesis of fluorosulfates and diphenyl sulfate.
X. Bai, L. Huang, P. Zhou, H. Xi, J. Hu, Z. Zuo, H. Feng, J. Org. Chem., 2022, 87, 4998-5004.


Vinylsilanes are stereoselectively converted into enamides by a sequence comprising epoxidation, nucleophilic ring opening of the resulting epoxysilanes with NaN3, and reduction of the azide, followed by a "one-pot" N-acylation/Peterson elimination process. This method is distinguished by its wide applicability.
A. Fürstner, C. Brehm, Y. Cancho-Grande, Org. Lett., 2001, 3, 3955-3957.


Vinylsilanes are stereoselectively converted into enamides by a sequence comprising epoxidation, nucleophilic ring opening of the resulting epoxysilanes with NaN3, and reduction of the azide, followed by a "one-pot" N-acylation/Peterson elimination process. This method is distinguished by its wide applicability.
A. Fürstner, C. Brehm, Y. Cancho-Grande, Org. Lett., 2001, 3, 3955-3957.


A palladium-catalyzed carbon-nitrogen bond-forming reaction of anilines and indoles with propargyl carbonates furnishes 2-amino-1,3-dienes in excellent yields under mild conditions and shows a broad functional group tolerance. The resulting 1,3-dienes are of great synthetic interest.
C. Q. O'Broin, P. J. Guiry, Org. Lett., 2020, 22, 879-883.


The use of (E)-2-methoxyethene-1-sulfonyl fluoride as sulfonyl fluoride reagent enables a highly atom-economical construction of enaminyl sulfonyl fluorides under mild and environmentally benign conditions with MeOH as the sole byproduct.


Orangoselenium catalysis enables an efficient route to 3-amino allylic alcohols in excellent regio- and stereoselectivity in the presence of a base. In the absence of bases α,β-unsaturated aldehydes were formed in excellent yield. The hydroxy group is crucial for the direct amination.
Z. Deng, J. Wei, L. Liao, H. Huang, X. Zhao, Org. Lett., 2015, 17, 1834-1837.


Nucleophilic addition of sulfonamides to 1-bromo-1-alkynes provided (Z)-N-(1-bromo-1-alken-2-yl)-p-toluenesulfonamides in good yield and in a highly regio- and stereoselective manner. A subsequent reaction in the presence of a palladium catalyst under Heck conditions afforded substituted pyrroles in good yield.
M. Yamagishi, K. Nishigai, T. Hata, H. Urabe, Org. Lett., 2011, 13, 4873-4875.


An efficient intermolecular trans-selective β-hydroamidation of ynamides provides (Z)-ethene-1,2-diamide derivatives with excellent regio- and stereo-selectivities for a wide range of substrates. The reaction proceeds under basic conditions in the absence of a transition-metal catalyst.
Z. Peng, Z. Zhang, Y. Tu, X. Zeng, J. Zhao, Org. Lett., 2018, 20, 5688-5691.


Rhodium(II) azavinyl carbenes, which are conveniently generated from 1-sulfonyl-1,2,3-triazoles, undergo a facile, mild, and convergent formal 1,3-insertion into N-H and O-H bonds of primary and secondary amides, various alcohols, and carboxylic acids to afford a wide range of vicinally bisfunctionalized (Z)-olefins with perfect regio- and stereoselectivity.
S. Chuprakov, B. T. Worrell, N. Selander, R. K. Sit, V. V. Fokin, J. Am. Chem. Soc., 2014, 136, 195-202.