Asymmetric Alkynylation of Seven-Membered Cyclic Imines by Combining Chiral Phosphoric Acids and Ag(I) Catalysts: Synthesis of 11-Substituted-10,11-dihydrodibenzo[<i>b</i>,<i>f</i>][1,4]oxazepine Derivatives

Asymmetric alkynylation of seven-membered cyclic imine dibenzo­[<i>b</i>,<i>f</i>]­[1,4]­oxazepines is successfully achieved by combining chiral phosphoric acid and Ag­(I) catalysts. Various arylacetylenes, conjugated enynes, and terminal 1,3-diynes are good substrates for this reaction, and aliphatic hexyne is also a suitable donor at elevated temperature. Optimization of this approach has provided a facile method to synthesize optically active 11-substituted-10,11-dihydro­dibenzo­[<i>b</i>,<i>f</i>]­[1,4]­oxazepine derivatives containing a carbon–carbon triple bond with 63–99% <i>ee</i>. Subsequent transformations of the carbon–carbon triple bond for the heterocyclic products have been disclosed

Asymmetric Alkynylation of Seven-Membered Cyclic Imines by Combining Chiral Phosphoric Acids and Ag(I) Catalysts: Synthesis of 11-Substituted-10,11-dihydrodibenzo[<i>b</i>,<i>f</i>][1,4]oxazepine Derivatives

Asymmetric alkynylation of seven-membered cyclic imine dibenzo­[b,f]­[1,4]­oxazepines is successfully achieved by combining chiral phosphoric acid and Ag­(I) catalysts. Various arylacetylenes, conjugated enynes, and terminal 1,3-diynes are good substrates for this reaction, and aliphatic hexyne is also a suitable donor at elevated temperature. Optimization of this approach has provided a facile method to synthesize optically active 11-substituted-10,11-dihydro­dibenzo­[b,f]­[1,4]­oxazepine derivatives containing a carbon–carbon triple bond with 63–99% ee. Subsequent transformations of the carbon–carbon triple bond for the heterocyclic products have been disclosed

Highly Enantioselective Pd-Catalyzed Asymmetric Hydrogenation of Activated Imines

Pd/bisphosphines complexes are highly effective catalysts for asymmetric hydrogenation of activated imines in trifluoroethanol. The asymmetric hydrogenation of N-diphenylphosphinyl ketimines 3 with Pd(CF3CO2)/(S)-SegPhos indicated 87−99% ee, and N-tosylimines 5 could gave 88−97% ee with Pd(CF3CO2)/(S)-SynPhos as a catalyst. Cyclic N-sulfonylimines 7 and 11 were hydrogenated to afford the useful chiral sultam derivatives in 79−93% ee, which are important organic synthetic intermediates and structural units of agricultural and pharmaceutical agents

Palladium-Catalyzed Asymmetric Hydrogenation of Functionalized Ketones

A novel catalytic system for asymmetric hydrogenation of functionalized ketones has been developed using a Pd/bisphosphine complex as the catalyst in 2,2,2-trifluoroethanol. The reaction exhibits high enantioselectivity, and up to 92.2% ee was obtained

Chiral Chalcogenide-Catalyzed Enantioselective Electrophilic Hydrothiolation of Alkenes

A new strategy for the construction of chiral sulfides by catalytic enantioselective hydrothiolation of alkenes via an electrophilic pathway has been developed. Using this strategy, cyclic and acyclic unactivated alkenes efficiently afforded various chiral products in the presence of electrophilic sulfur reagents and silanes through chiral chalcogenide catalysis. The obtained products were easily transformed into other types of valuable chiral sulfur-containing compounds. Mechanistic studies revealed that the superior construction of chiral thiiranium ion intermediate is the key to achieving such a transformation

Enantioselective Synthesis of Cyclic Sulfamidates via Pd-Catalyzed Hydrogenation

Using Pd(CF3CO2)2/(S,S)-f-binaphane as the catalyst, an efficient enantioselective synthesis of cyclic sulfamidates was developed via asymmetric hydrogenation of the corresponding cyclic imines in 2,2,2-trifluoroethanol at room temperature with high enantioselectivities (up to 99% ee)

Synthesis of Carboranylated Dihydropyrrolo[1,2‑<i>a</i>]quinoxalines and Dihydroindolo[1,2‑<i>a</i>]quinoxalines by BF₃·OEt₂-Catalyzed Heterocyclization of <i>C</i>‑Formyl‑<i>o</i>‑carboranes and Investigation of Their Oxidation Stability

A BF3·OEt2-catalyzed synthesis of carboranylated dihydropyrrolo­[1,2-a]­quinoxalines and dihydroindolo­[1,2-a]­quinoxalines in 30–99% yields is presented through the heterocyclization of various C-modified C-formyl-o-carboranes with 1-(2-aminophenyl)-pyrroles/indoles. A systematic comparative investigation of their oxidation stability in air confirmed that 4-carboranyl-4,5-dihydropyrrolo­[1,2-a]­quinoxaline had better stability than the 4-phenyl analogue. A cage-deboronation reaction for N-acetyl-substituted carboranylated dihydropyrrolo­[1,2-a]­quinoxaline produced the corresponding 7,8-nido-carborane cesium salt. A kinetic resolution was also realized to obtain an optically pure carboranylated N-heterocycle scaffold bearing a carborane cage carbon-bonded chiral stereocenter

Synthesis of Carboranylated Dihydropyrrolo[1,2‑<i>a</i>]quinoxalines and Dihydroindolo[1,2‑<i>a</i>]quinoxalines by BF₃·OEt₂-Catalyzed Heterocyclization of <i>C</i>‑Formyl‑<i>o</i>‑carboranes and Investigation of Their Oxidation Stability

A BF3·OEt2-catalyzed synthesis of carboranylated dihydropyrrolo­[1,2-a]­quinoxalines and dihydroindolo­[1,2-a]­quinoxalines in 30–99% yields is presented through the heterocyclization of various C-modified C-formyl-o-carboranes with 1-(2-aminophenyl)-pyrroles/indoles. A systematic comparative investigation of their oxidation stability in air confirmed that 4-carboranyl-4,5-dihydropyrrolo­[1,2-a]­quinoxaline had better stability than the 4-phenyl analogue. A cage-deboronation reaction for N-acetyl-substituted carboranylated dihydropyrrolo­[1,2-a]­quinoxaline produced the corresponding 7,8-nido-carborane cesium salt. A kinetic resolution was also realized to obtain an optically pure carboranylated N-heterocycle scaffold bearing a carborane cage carbon-bonded chiral stereocenter