Catalytic Asymmetric Synthesis of Chiral γ‑Amino Ketones via Umpolung Reactions of Imines

The first direct catalytic asymmetric synthesis of γ-amino ketones was realized by the development of a highly diastereoselective and enantioselective C–C bond-forming umpolung reaction of imines and enones under the catalysis of a new cinchona alkaloid-derived phase-transfer catalyst. In a loading ranging from 0.02 to 2.5 mol %, the catalyst activates a broad range of trifluoromethyl imines and aldimines as nucleophiles to engage in chemo-, regio-, diastereo- and enantioselective C–C bond-forming reactions with acyclic and cyclic enones, thereby converting these readily available prochiral starting materials into highly enantiomerically enriched chiral γ-amino ketones in synthetically useful yields. Enabled by this unprecedented umpolung reaction of imines, conceptually new and concise routes were developed for the asymmetric synthesis of nitrogen-heterocycles such as pyrrolidines and indolizidines

Catalytic Asymmetric Synthesis of Chiral γ‑Amino Ketones via Umpolung Reactions of Imines

The first direct catalytic asymmetric synthesis of γ-amino ketones was realized by the development of a highly diastereoselective and enantioselective C–C bond-forming umpolung reaction of imines and enones under the catalysis of a new cinchona alkaloid-derived phase-transfer catalyst. In a loading ranging from 0.02 to 2.5 mol %, the catalyst activates a broad range of trifluoromethyl imines and aldimines as nucleophiles to engage in chemo-, regio-, diastereo- and enantioselective C–C bond-forming reactions with acyclic and cyclic enones, thereby converting these readily available prochiral starting materials into highly enantiomerically enriched chiral γ-amino ketones in synthetically useful yields. Enabled by this unprecedented umpolung reaction of imines, conceptually new and concise routes were developed for the asymmetric synthesis of nitrogen-heterocycles such as pyrrolidines and indolizidines

Copper-Catalyzed Electrophilic Polyhydroamination of Internal Alkynes

Polyhydroamination of alkynes is an important methodology for preparing nitrogen-containing polymers. At present, all of the reported polyhydroamination of alkynes proceed through nucleophilic addition, and no straightforward electrophilic polyhydroamination has been reported. In this paper, a novel copper-catalyzed electrophilic polyhydroamination of alkynes was developed, and soluble and thermally stable poly­(enamine)­s with high weight-average molecular weights (<i>M</i>_ws, up to 12 650) were produced in excellent yields (up to 95%) under mild reaction conditions. Moreover, the regioselectivity of this electrophilic polyhydroamination could be tuned by adjusting one of the substitutions of internal diynes from phenyl to alkyl group. By introducing the tetraphenylethene moiety into polymer backbones, the resultant polymers exhibit unique aggregation-induced emission feature, and their aggregates could be used to sensitively detect explosives. This efficient polymerization will open up enormous opportunities for preparing functional nitrogen-containing acetylenic polymers applicable in diverse areas

Pd-Catalyzed γ‑C(sp³)–H Arylation of Free Amines Using a Transient Directing Group

Pd­(II)-catalyzed γ-C­(sp³)–H arylation of primary amines is realized by using 2-hydroxy­nicotinaldehyde as a catalytic transient directing group. Importantly, the catalyst and the directing group loading can be lowered to 2% and 4% respectively, thus demonstrating high efficiency of this newly designed transient directing group. Heterocyclic aryl iodides are also compatible with this reaction. Furthermore, swift synthesis of 1,2,3,4-tetrahydro­naphthyridine derivatives is accomplished using this reaction

Versatile Alkylation of (Hetero)Aryl Iodides with Ketones via β‑C(sp³)–H Activation

We report Pd­(II)-catalyzed β-C­(sp³)–H (hetero)­aryl­ation of a variety of ketones using a commercially available 2,2-dimethyl amino­oxy­acetic acid auxiliary. Facile installation and removal of the auxiliary as well as its superior scope for both ketones and (hetero)­aryl iodides overcome the significant limitations of the previously reported β-C­(sp³)–H arylation of ketones. The ready availability of ketones renders this reaction a broadly useful method for alkyl–(hetero)­aryl coupling involving both primary and secondary alkyls

Spontaneous Amino-yne Click Polymerization: A Powerful Tool toward Regio- and Stereospecific Poly(β-aminoacrylate)s

Efficient synthesis of poly­(enamine)­s has been a great challenge because of their poor stability, poor solubility, and low molecular weights. In this work, a spontaneous amino-yne click polymerization for the efficient preparation of poly­(enamine)­s was established, which could proceed with 100% atom efficiency under very mild conditions without any external catalyst. Through systematic optimization of the reaction conditions, several soluble and thermally stable poly­(β-aminoacrylate)­s with high molecular weights (<i>M</i>_w up to 64400) and well-defined structures were obtained in excellent yields (up to 99%). Moreover, the polymerization can perform in a regio- and stereospecific fashion. Nuclear magnetic resonance spectra analysis revealed that solely anti-Markovnikov additive products with 100% <i>E</i>-isomer were obtained. The reaction mechanism was well demonstrated with the assistance of density functional theory calculations. In addition, by introducing the tetraphenylethene moiety, the resulting polymers exhibit unique aggregation-induced emission characteristics and could be applied in explosives detection and bioimaging. This polyhydroamination is a new type of click polymerization and opens up enormous opportunities for preparing functional polymeric materials