Synthesis in stereo: The first total synthesis of papuamide B, a cyclic peptide isolated from a marine sponge, has been achieved. The configuration of three stereogenic centers of its dienoic acid ...unit has been established by comparison to a series of stereoisomers of known configuration, and the stereochemistry of its 2,3‐diaminobutanoic acid segment has been revised.
A bio-inspired synthesis of hybrid flavonoids from 2-hydroxylchalcone is described. Under the irradiation of 24 W CFL, 2-hydroxychalcone reacts with various nucleophiles to deliver structurally ...diverse hybrid flavonoids in good to excellent yields in the presence of a catalytic Brønsted acid. Moreover, moderate enantioselectivities could be obtained using a catalytic chiral phosphoric acid
via
counter anion directed addition. Based on mechanistic studies, the reaction is proposed to proceed
via
tandem double-bond isomerization/dehydrated cyclization of 2-hydroxychalcone to form a transient flavylium cation, which is
in situ
captured by nucleophiles to afford hybrid flavonoids.
An efficient protocol for the synthesis of hybrid flavonoids was achieved
via
a bio-inspired tandem reaction of 2-hydroxychalcone with various nucleophiles.
A novel class of crystalline porous materials has been developed utilizing multilevel dynamic linkages, including covalent B−O, dative B←N and hydrogen bonds. Typically, boronic acids undergo in situ ...condensation to afford B3O3‐based units, which further extend to molecular complexes or chains via B←N bonds. The obtained superstructures are subsequently interconnected via hydrogen bonds and π–π interactions, producing crystalline porous organic frameworks (CPOFs). The CPOFs display excellent solution processability, allowing dissolution and subsequent crystallization to their original structures, independent of recrystallization conditions, possibly due to the diverse bond energies of the involved interactions. Significantly, the CPOFs can be synthesized on a gram‐scale using cost‐effective monomers. In addition, the numerous acidic sites endow the CPOFs with high NH3 capacity, surpassing most porous organic materials and commercial materials.
A novel class of crystalline porous organic frameworks (CPOFs) are prepared based on covalent B−O, dative B←N and hydrogen bonds. Furthermore, gram‐scale production can be achieved at low cost, alongside excellent solution processibility, paving the way to diverse applications. Remarkably, the CPOFs exhibit exceptionally high NH3 uptake capacities, indicating their great potential toward NH3 capture.
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•R2O7 is capable of promoting dehydration of monoallylic diols.•Short reaction time and no need of cautious exclusion of water and oxygen.•High E-olefin selectivity.•Wide substrate ...scope.
A Re2O7 catalyzed cycloetherification of monoallylic diols is described. The reaction features short reaction time, mild reaction conditions and exclusive E selectivity. A wide range of monoallylic alcohols with alkyl or aryl substituents on olefin smoothly undergo ring closure to deliver corresponding oxa-heterocycles. The reaction is also operationally simple and not sensitive to air and moisture.
Construction of continuous all-carbon quaternary centers via intramolecular oxidative coupling was described. Intramolecular oxidative coupling of bisoxindole linked by diol derived from d-tartaric ...acid diastereoselectively produced C1 or C2 isomers of the annulation product. The selectivity was realized by judiciously choosing base and solvent employed in the reaction. As key intermediates for the synthesis of cyclotryptamine alkaloids, the resulting bisoxindole should be applicable to the total syntheses of complex indole alkaloids with continuous all-carbon quaternary centers.
Isocyanide insertion: the first rhodium-catalyzed annulation of
N
-benzoylsulfonamide incorporating with isocyanide via C-H activation is described. The transformation is broadly compatible with
N
...-benzoylsulfonamides bearing various electron-properties as well as isocyanides. From practical point of view, this methodology provides the most straightforward approach to a series of 3-(imino)isoindolinones.
The dienone-phenol rearrangement of 4,4-disubstituted cyclohexadienones catalyzed by Re 2 O 7 has been described. Multi-substituted phenols can be efficiently obtained in good to excellent yields by ...employing this catalytic protocol.
By designing a novel chiral ion-pair organocatalyst composed of chiral phosphate and DABCO-derived quaternary ammonium, highly enantioselective 3-
exo
iodo-cycloetherification of allyl alcohols was ...achieved using NIS as a halogen source. Based on this reaction, one-pot asymmetric 3-
exo
iodo-cycloetherification/Wagner-Meerwein rearrangement of allyl alcohols en route to enantioenriched 2-iodomethyl-2-aryl cycloalkanones was subsequently developed. Due to the participation of adjacent iodine, the Wagner-Meerwein rearrangement of 2-iodomethyl-2-aryl epoxide proceeds with unusual retention of stereoconfiguration.
Enantioselective 3-
exo
iodo-cycloetherification of allyl alcohols was realized by employing a novel ion-pair organocatalyst.
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