Photoredox-Catalyzed Metal-Free Regio-&Stereoselective C(sp^(2))-H Amination of Enamides with N-Aminopyridium Salts

A visible-light-induced photoredox-catalyzed regioselective and stereoselective C(sp')-H amination of enamides with bench-stable and A visible-light-induced photoredox-catalyzed regioselective and stereoselective C(sp)-H amination of enamides with bench-stable and easily accessible N-aminopyridium salts is developed,affording synthetically and biologically prominent vicinal 1,2-diamine scaffolds with broad substrate scope and excellent functional group compatibility.The transformation proceeded through a radical pathway involving the Giese addition of the relatively electrophilic N-centered sulfonamidyl radical species to nucleophilicβ-olefinic position of enamides followed by the ensuing single electron oxidation andβ-H elimination,delivering geometrically-defined Z-configuredβ-sulfonamidylated enamides.The operational simplicity,environmental friendliness and cost efficiency of this methodology allowed it to pave a new avenue to enrich the arsenal of synthetically crucial functionalized enamides and their related derivatives.

Charge transfer complex enabled photoreduction of ether phosphonium salts for the selective oxyalkylation of enamides

A charge transfer complex(CTC)-enabled photoreduction of ether phosphonium salts for the generation of oxyalkyl radicals was described.The photoreduction provides a convenient method to achieve selective oxyalkylation of enamides with broad substrate scope.The method features operational simplicity,mild and inherent green conditions.

Access to multi-functionalized oxazolines via silver-catalyzed heteroannulation of enamides with sulfoxonium ylides

Disclosed herein is an efficient Ag-catalyzed 4+1 heteroannulation reaction of enamides withα-carbonyl sulfoxonium ylides.The diastereoselective transformation provides a practical access to a diverse range of multi-functionalized oxazoline derivatives.The synthetic utility of the resultant tetrasubstituted oxazolines is further demonstrated by a series of useful manipulations into valuable building blocks of pharmaceutical relevance.

Copper-Catalyzed Direct Oxyphosphorylation of Enamides with P（O）-H Compounds and Dioxygen

A simple and convenient copper-catalyzed direct oxyphosphorylation of enamides with P（O）-H compounds and dioxygen has been developed under mild conditions. This methodology can allow the synthesis of a series of valuable β-ketophosphine oxides β-ketophosphonates in moderate to good yields with a broad substrate scope simply by using readily-available starting materials.

Palladium-catalyzed oxidative cyclopropanation of enamides and norbornenes initiated by C–H activation

A novel palladium-catalyzed oxidative cyclopropanation of enamides and norbornenes has been developed. The reaction proceeded through palladium-catalyzed vinyl C–H bond activation of enamides followed by two migratory insertions, β-(N)H elimination and hydrolyzation cascade steps. The reaction tolerates a range of functional groups and provides an effective method for the synthesis of cyclopropane-fused norbornanes in good yields under mild conditions.

PhI(OAc)2-promoted umpolung acetoxylation of enamides for the synthesis of α-acetoxy ketones

Umpolung is a fundamental concept in organic chemistry, which provides an alternative strategy for the synthesis of target compounds which were not easily accessible by conventional methods. Herein, a mild and efficient PhI(OAc)_2-promoted umpolung acetoxylation reactions of enamides was developed for the synthesis of α-acetoxy ketones. The reaction tolerates a wide range of functional groups and affords α-acetoxy ketones in good to excellent yields. PhI(OAc)_2 serves as a source of acetoxy in the reaction.

Visible-light-promoted and photocatalyst-free trifluoromethylation of enamides

An efficient and practical method is developed for the trifluoromethylation of enamides using Umemoto's reagent as the trifluoromethylating reagent. These reactions proceeded under visible light irradiation without any photocatalyst at room temperature in good chemical yields.

Enantioselective Rh-Catalyzed Hydrogenation of N-Acyl Dehydroamino Esters and Enamides with Monodentate Phosphoramidite Ligands

Chiral monodentate phosphoramidite ligands were conveniently prepared from 1,1＇-bi-2-naphthol （BINOL） and （S）-pyrrolidine in good yields, which were effective chiral ligands in the enantioselective rhodium-catalyzed hydrogenation of dehydroamino esters and enamides at low hydrogenation pressure. High conversion rate （up to 99% for dehydroamino esters and enamides） and good enantioselectivity （up to 96.3% ee for dehy- droamino esters and 91.7% ee for enamides） were obtained.

Asymmetric Spirocyclization Enabled by Iridium and Brønsted Acid-Catalyzed Formal Reductive Cycloaddition

A catalytic,enantioselective spirocyclization of formanilides or formylindolines and enamides has been developed herein.The reaction proceeds through a sequential iridium-catalyzed hydrosilylation of tertiary formanilides and a chiral phosphoric acid-catalyzed formal cycloaddition of exocyclic enamides,thus providing straightforward access to a diverse array of enantioenriched azaspirocycles under mild conditions.

Et2Zn-promoted β-trans-selective hydroboration of ynamide

The trans-hydroboration of alkyne represents a challenging task in organic synthesis.Reported herein is an Et2 Zn promotedβ-trans hydroboration of ynamides by using N-heterocyclic carbene(NHC)-ligated borane as boryl source.The reaction leads to a stereoselective construction of enamides bearing a valuable boryl substituent.Both aromatic and aliphatic ynamides were applicable to the reaction.Synthetic transformation of the C-B bond in the product via Suzuki-Miyaura coupling provides a simple and stereospecific route to multi-substituted enamides.Mechanistic studies were conducted and the possible mechanism was discussed.