Search

An asymmetric cascade allylation/spiroketalization reaction between 2-(1-hydroxyallyl)phenols and 5-methyleneoxazolines is accomplished by using a chiral Ir(I) catalyst derived from commercially available iridium precursor and the Carreira ligand. This protocol furnishes a class of structurally novel and unique oxazoline-spiroketals in up to 86% yield,99% ee and20:1 dr. Moreover, control experiments reveal that 4,4-disubstitution on 5-methyleneoxazolines is necessary to avoid the aromatization and for the spiroketalization to occur. On the basis of this, a plausible reaction mechanism is illustrated.

An iridium-catalyzed trifluoroacetic acid-promoted asymmetric cascade allylation/Pictet-Spengler cyclization reaction of azomethine ylides with aromatic allylic alcohols is reported. This protocol provides a facile and scalable method for the construction of 1,3,4-trisubstituted tetrahydroisoquinolines containing two stereogenic centers in good yields (up to 96%) with generally excellent diastereo- and enantioselectivities (up to >20:1 dr and >99% ee). Furthermore, a series of aromatic heterocycle-fused piperidines were also obtained with excellent enantiocontrol by this methodology.

The palladium-catalyzed asymmetric [4 + 3] cycloaddition of a sulfonyl-trimethylenemethane (TMM) donor with azadienes furnished various sulfonyl-fused azepines with exclusive regioselectivities and excellent stereoselectivities (up to >20:1 dr, >99% ee) in high yields (up to 93%). Moreover, sulfone, serving as a transient activating group of the TMM species, can be easily removed from the cycloadducts to provide the structurally simple fused azepines with excellent enantioselectivities. This strategy demonstrates sulfonyl-TMM as an effective surrogate of naked TMM with high reactivity, exclusive regioselectivity, and excellent stereoselectivity.

An N-confused hexapyrrolic phlorinoid 1 and its isomer N-fused hexapyrrolic phlorinoid 2 were synthesized through [4 + 2] condensation. Both 1 and 2 can be readily transformed into N-confused hexapyrrolic phlorinone 3 under aerobic conditions. Coordination of 1 with Cu(acac)2 afforded two different mono-Cu(II) complexes 4 and 5 with CNNN and ONNN coordination environments, respectively. The NIR absorption bands can be effectively modulated up to 1265 nm through the oxidation, fusion, and metalation reactions.

A regiodivergent organocatalytic enantioselective Michael addition/three-atom ring expansion sequence of electron-withdrawing group activated cyclobutanones with 2-nitrovinylindoles was developed. ...

A catalyst-, oxidant-, electrolyte-free method for the preparation of α-ketoamides through the direct electrochemical amidation of α-ketoaldehydes and amines with innocuous hydrogen as the sole byproduct at ambient temperature was developed. The present reaction features clean and mild conditions, excellent functional-group tolerance, and high atom economy and scalability, enabling facile applications in pharmaceutical chemistry.

An organocatalytic asymmetric arylmethylation/N-hemiacetalization of 2-indolyl methane derivatives and 2-enals was developed. Notably, the 2-methyl of indole was readily deprotonated to produce highly reactive nucleophilic species by introducing the nitro group at the C3 position of the indole ring. A spectrum of valuable chiral dihydropyrido[1,2-a]indoles were efficiently constructed with excellent enantioselectivity (up to >99% ee). Furthermore, the corresponding products could be easily functionalized via simple deprotonation and treatment with other electrophiles with excellent diastereoselectivities (>20:1 dr).

A highly enantioselective Michael/lactonization cascade reaction of 3-hydroxyoxindoles with 3-trifluoroethylidene oxindoles was developed. The use of a cinchona-derived squaramide catalyst is essential in achieving high diastereo- and enantioselectivities. This reaction represents the first example of intramolecular amide C–N bond cleavage and lactonization of 3-hydroxyoxindoles with 3-trifluoroethylidene oxindoles, which provides an efficient and convenient approach to diverse CF3-containing spirooxindole γ-lactones in high yields and good to excellent diastereo- and enantioselectivities.

A catalytic asymmetric decarboxylative [3 + 2] annulation via indolyl copper-allenylidene amphiphilic intermediates has been developed. This protocol offers a straightforward method for the synthesis of biologically important pyrrolo[1,2-a]indoles bearing contiguous quaternary and tertiary stereogenic centers with excellent diastereo- and enantioselectivities (up to >20:1 dr and >99% ee). In addition, the diversity-oriented synthesis of pyrrolo[1,2-a]indoles was achieved via versatile transformations of the alkyne-containing cycloadducts.

An organocatalytic asymmetric arylmethylation/

A highly enantioselective Michael/lactonization cascade reaction of 3-hydroxyoxindoles with 3-trifluoroethylidene oxindoles was developed. The use of a cinchona-derived squaramide catalyst is essential in achieving high diastereo- and enantioselectivities. This reaction represents the first example of intramolecular amide C-N bond cleavage and lactonization of 3-hydroxyoxindoles with 3-trifluoroethylidene oxindoles, which provides an efficient and convenient approach to diverse CF

A highly diastereo- and enantioselective desymmetrization of prochiral cyclopropenes via a Cu(CH3CN)4BF4/Ph-Phosferrox complex catalyzed 1,3-dipolar cycloaddition of azomethine ylides was described. A variety of complex 3-azabicyclo[3.1.0]hexane derivatives bearing five contiguous stereogenic centers and two all-carbon quaternary stereogenic centers were directly synthesized as a single isomer in excellent yields (up to 99%) and enantioselectivities (97 → 99% ee). Notably, various functional groups (CO2R, CN, CONMe2, and Ph) of cyclopropenes were found to be well-tolerated in this transformation. The cycloadduct was conveniently converted to a biologically important GABA derivative via LiAlH4 reduction and subsequent hydrolysis.

A highly efficient copper(I)-catalyzed asymmetric 1,3-dipolar cycloaddition of azomethine ylides with 3-silyl unsaturated esters has been developed, providing elegant access to chiral 3-silylpyrrolidine derivatives bearing contiguous stereogenic centers in moderate-to-excellent yields (up to 99%) with high diastereo- and enantioselectivities (dr up to >99:1; ee up to 96%). Notably, the 3-silylpyrrolidines can easily be converted to pyrrolidine azasugar derivatives with potential biological activities by the reduction of two ester groups and carbon–silicon bond oxidation.

A highly efficient asymmetric 1,3-dipolar cycloaddition of azomethine ylides to 5-alkylidene thia(oxa)zolidine-2,4-diones catalyzed by a chiral N,O-ligand/Cu(CH3CN)4BF4 system is reported, affording structurally novel spirocyclic pyrrolidine-thia(oxa)zolidinediones with a spiro-heteroquaternary stereogenic center in good to excellent yields (up to 99%), with excellent levels of diastereo- and enantioselectivity (dr up to 99:1; ee up to 98%).