Search

The difunctionalization of unsaturated bonds plays a vital role in the enrichment of molecular complexity. While various catalytic methods for alkene and alkyne difunctionalization have been developed in recent years, hetero‐functionalization the introduction of two different atoms has been less explored. This is mainly due to the challenges associated with achieving high chemo‐, regio‐, and stereoselectivity, especially when adding two similar atoms from the same group across unsaturated bonds. In this study, we describe a nickel‐catalyzed, three‐component reductive protocol for group 14 element hetero‐difunctionalization of 1,3‐enynes using electrochemistry. This new method is mild, selective, and general, allowing for the silyl‐, germanyl‐, and stannyl‐alkylation of enynes. Various chlorosilanes as well as chlorogermans, and chlorostannanes can be successfully used in combination with aryl/alkyl‐substituted 1,3‐enynes and primary, secondary, and tertiary alkyl bromides in the electroreductive coupling. [ABSTRACT FROM AUTHOR]

Herein, we report a reductive cross‐coupling reaction of α‐oxy halides, simply generated from aldehydes, with a series of C(sp2)‐ and C(sp)‐electrophiles. A wide range of aryl and heteroatom aryl halides, vinyl bromides, alkynyl bromides, and acyl chlorides react with unhindered and hindered aldehyde‐derived α‐oxy halides by providing protected alcohols as well as α‐hydroxy ketones. Noteworthy, the reductive couplings are achieved not only through thermal catalysis with the use of metal reductants but also by photocatalysis, electrochemistry, and mechanochemistry. The unrestricted interchange of the four strategies indicates their underlying mechanistic similarities. The generation of NiI intermediate is proposed to be the key point for ketyl radical formation via a single‐electron transfer (SET) event, which was rationalized by an array of control experiments and density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

Trisubstituted alkenes are important organic synthons and have broad applications in the synthesis of many pharmaceuticals and materials. The stereoselective synthesis of such compounds has long been a research focus for organic researchers. Herein, we report a three-component, reductive cascade, cross-coupling reaction for the arylalkylation of alkynes. A wide range of trisubstituted alkenes are obtained in good to high yields with excellent chemo- and stereoselectivity by switching between electrochemistry and photocatalysis. The E isomer of the product is obtained exclusively when the reaction is conducted with electricity and nickel, while the Z isomer is generated with high stereoselectivity when photo- and nickel dual catalysts are used. Moreover, photo-assisted electrochemically enabled nickel catalyzed protocol is demonstrated to selectively deliver Z-trisubstituted alkenes without the addition of photocatalysts. The construction of trisubstituted alkenes with high stereoselectivity is challenging. Here, the authors realize the stereodivergent synthesis of such compounds via switching between electrochemistry, photochemistry and photoelectrochemistry. [ABSTRACT FROM AUTHOR]

The formation of C‐heteroatom bonds represents an important type of bond‐forming reaction in organic synthesis and often provides a fast and efficient access to privileged structures found in pharmaceuticals, agrochemical and materials. In contrast to conventional Pd‐ or Cu‐catalyzed C‐heteroatom cross‐couplings under high‐temperature conditions, recent advances in homo‐ and heterogeneous Ni‐catalyzed C‐heteroatom formations under mild conditions are particularly attractive from the standpoint of sustainability and practicability. The generation of NiIII and excited NiII intermediates facilitate the reductive elimination step to achieve mild cross‐couplings. This review provides an overview of the state‐of‐the‐art approaches for mild C‐heteroatom bond formations and highlights the developments in photoredox and nickel dual catalysis involving SET and energy transfer processes; photoexcited nickel catalysis; electro and nickel dual catalysis; heterogeneous photoredox and nickel dual catalysis involving graphitic carbon nitride (mpg‐CN), metal organic frameworks (MOFs) or semiconductor quantum dots (QDs); as well as more conventional zinc and nickel dual catalyzed reactions. [ABSTRACT FROM AUTHOR]

We demonstrate the construction of a dual-mode biosensor based on fully-π conjugated covalent organic framework (COF) and cobalt oxyhydroxide (CoOOH) nanoflakes for electrochemiluminescent (ECL) and electrochemical sensing of alkaline phosphatase (ALP). The fully-π conjugated COF with sp2 carbon-linkage is synthesized through Knoevenagel polycondensation of 2, 5-dimethoxy-terephthalaldehyde (DMTA) and 1,3,5-tris(4-cynomethylphenyl)benzene (TCPB), and it acts as an efficient ECL emitter whose signal is 41 and 125-fold higher than those of TCPB and DMTA. The ECL signal of TCPB-DMTA-COF may be quenched by CoOOH nanoflakes through electrochemiluminescent resonance energy transfer, and meanwhile CoOOH promotes the oxidation of o-phenylenediamine (o -PD) to generate a high differential pulse voltammetry (DPV) signal. When ALP is present, it hydrolyzes L -ascorbic acid-2-phosphate (AAP) to produce L -ascorbic acid (AA). AA can reduce CoOOH to Co2+, resulting in the decomposition of the CoOOH nanoflakes and consequently the recovery of ECL signal and the decrease of DPV peak current. This dual-mode biosensor can efficiently eliminate the errors associated with personnel operation and experimental factors, leading to more reliability and accuracy than single-mode biosensor. Moreover, this dual-mode biosensor can be applied for specifically sensing ALP in human serums and screening the inhibitors, with potential applications in biomedical researches. • We construct a dual-mode biosensor based on fully-π conjugated covalent organic framework and cobalt oxyhydroxide nanoflakes. • This dual-mode biosensor enables electrochemiluminescent and electrochemical sensing of alkaline phosphatase. • This dual-mode biosensor can be applied for specifically sensing ALP in human serums. • This dual-mode biosensor can be used for screening the inhibitors [ABSTRACT FROM AUTHOR]