Syntheses of α-Stannylated and α-Iodinated Enamides via Molybdenum-Catalyzed Hydrostannation

Regio- and Stereocontrolled Hydrohalogenation of Ynamides with N-Halosuccinimides (NXS) as the Halogen Source: Synthesis of (E)-α-Haloenamides

Presented herein is a facile stereoselective construction of synthetically versatile chiral and achiral (E)-α-haloenamides under mild conditions utilizing N-halosuccinimides and diphenylphosphine oxide. This reaction is metal-free, mild, efficient, very rapid, and practical and highlights the synthetic versatility of ynamides. The reaction has a broad substrate scope; both chiral and achiral ynamides have been transformed into the corresponding (E)-α-haloenamides within a very short period of time without compromising selectivity or complexity.

Iron-Catalyzed Regiodivergent Hydrostannation of Alkynes: Intermediacy of Fe(IV)-H versus Fe(II)-Vinylidene

We report an iron system, Cp*Fe(1,2-R₂PC₆H₄X), which controls the Markovnikov and anti-Markovnikov hydrostannation of alkynes by tuning the ionic metal-heteroatom bonds (Fe-X) reactivity. The sequential addition of nBu₃SnH to the iron-amido catalyst (1, X = HN^-, R = Ph) affords a distannyl Fe(IV)-H species responsible for syn-addition of the Sn-H bond across the C≡C bond to produce branched α-vinylstannanes. Activation of the C(sp)-H bond of alkynes by an iron-aryloxide catalyst (2, X = O^-, R = Cy) affords an iron(II) vinylidene intermediate, allowing for gem-addition of the Sn-H to the terminal-carbon producing β-vinylstannanes. These catalytic reactions exhibit excellent regioselectivity and broad functional group compatibility and enable the large-scale synthesis of diverse vinylstannanes. Many new reactions have been established based on such a synthetic Fe-X platform to demonstrate that the initial step of the catalysis is conveniently controlled by the activation of either the tin hydride or the alkyne substrate.

Convergent and Stereoselective Method for the Synthesis of Acyclic α-Chloroenamides

A direct, stereocontrolled synthesis of acyclic α-chloroenamides is presented. Our methodology showed good yields and substrate scope. Mechanistic insights are provided that account for the high levels of stereoselectivity reported. Subsequent synthetic manipulation of the α-chloroenamides provides direct entry to polyfunctionalized acyclic enamides, compounds of wide use in organic chemistry and the pharmaceutical industry.

Catalyst-Free [4+2] Cycloaddition of Ynamides with 2-Halomethyl Phenols To Construct 2-Amino-4H-Chromenes and α-Halo Enamides Simultaneously

We report the development of a facile protocol for the [4+2] cycloaddition of ynamides and 2-halomethyl phenols to afford the corresponding 2-amino-4H-chromenes and α-halo enamides under catalyst-free conditions. The reaction proceeds under mild conditions and exhibits good tolerance toward various functional groups and generates high yields. The plausible mechanism involves the formation of an active intermediate keteniminium as well as o-methylene quinone.

Isonitriles as supporting and non-innocent ligands in metal catalysis

Isonitriles are unique ligands for metal catalysis, owing to the possibility of their steric and electronic tuning as well as their non-innocent nature to undergo transformations with nucleophiles.

A Highly Regio- and Stereoselective Syntheses of α-Halo Enamides, Vinyl Thioethers, and Vinyl Ethers with Aqueous Hydrogen Halide in Two-Phase Systems

A metal-free regio- and stereoselective method is achieved for the preparation of ( E)-configured α-halo enamides, vinyl thioethers, and vinyl ethers using aqueous HX (X = F, Cl, Br, I), which features high functional group compatibility and regio- and stereoselectivity, mild conditions, high efficiency, and rapid transformation. Additionally, the isomers could be yielded readily from the ( E)-configured α-halo enamides via photocatalysis or under Sonogashira coupling conditions.

Triphenylphosphine promoted regio and stereoselective α-halogenation of ynamides

Metal free α-halogenation of ynamides at room temperature.

Preparation of (Z)-α,β-disubstituted enamides via palladium-catalyzed addition of boronic acids to ynamides

A Pd-catalyzed, highly regio- and stereoselective addition of boronic acids to ynamides has been realized. This protocol generates (Z)-α,β-disubstituted enamides in high yields with excellent regio- and stereoselectivity under the mild reaction conditions, thereby providing a good complementary method for the diverse synthesis of multifunctional enamides. A wide collection of functional groups are found to be tolerated. It represents a straightforward and useful means to assemble stereodefined enamides from readily available starting materials.