Since R. C. Fuson formulated the principle of vinylogy, this platform has been extensively developed through combining diverse predominant chemical transformations. Among them, asymmetric vinylogous ...Michael reaction has been recognized as an efficient method to build chiral 1,7‐dioxo C chains (1,9‐dioxo C chains for bisvinylogous manifold) with diverse functional groups, which provides robust approaches to access numerous chiral compounds with pharmaceutical importance. In this review, the advances in the area of organocatalytic asymmetric vinylogous Michael reactions on the period from 2014 to nowadays are discussed, including the current scope, limitations of the transformations and applications in asymmetric synthesis of complex and valuable compounds.
Asymmetric vinylogous Michael reaction has been recognized as an efficient method to build chiral 1,7‐ and 1,9‐dioxo C chains with diverse functional groups, which provides robust approaches to numerous chiral multifunctional compounds with pharmaceutical importance. In this review, the advances of organocatalytic asymmetric vinylogous Michael reactions on the period from 2014 to nowadays are discussed.
J-aggregation is an efficient strategy for the development of fluorescent imaging agents in the second near-infrared window. However, the design of the second near-infrared fluorescent J-aggregates ...is challenging due to the lack of suitable J-aggregation dyes. Herein, we report meso-2.2paracyclophanyl-3,5-bis-N,N-dimethylaminostyrl BODIPY (PCP-BDP2) as an example of BODIPY dye with J-aggregation induced the second near-infrared fluorescence. PCP-BDP2 shows an emission maximum at 1010 nm in the J-aggregation state. Mechanism studies reveal that the steric and conjugation effect of the PCP group on the BODIPY play key roles in the J-aggregation behavior and photophysical properties tuning. Notably, PCP-BDP2 J-aggregates can be utilized for lymph node imaging and fluorescence-guided surgery in the nude mouse, which demonstrates their potential clinical application. This study demonstrates BODIPY dye as an alternate J-aggregation platform for developing the second near-infrared imaging agents.
With the development of organic optoelectronic materials and bioimaging technology, to exploit organic luminescent materials with high luminescent efficiency in aggregation-state has become a ...research hotspot. BODIPYs have become one of the research objects of this kind of material because of their obvious advantages. This review focuses on the design and synthesis of AIE-type BODIPYs, the mechanism of AIE properties and their applications in recent years. Through classification, analysis, and summary, this review aims to explore the structure-activity relationship of AIE-type BODIPYs and to provide ideas for the further design and potential applications of AIE-active fluorescent materials.
Classic nucleophilic substitution reactions (S
1 and S
2) are not generally amenable to the enantioselective variants that use simple and racemic alkyl halide electrophiles. The merging of transition ...metal catalysis and radical chemistry with organometallic nucleophiles is a versatile method for addressing this limitation. Here, we report that visible light-driven catalytic asymmetric photoredox radical coupling can act as a complementary and generic strategy for the enantioconvergent formal substitution of alkyl haldies with readily available and bench-stable organic molecules. Single-electron reductive debrominations of racemic α-bromoketones generate achiral alkyl radicals that can participate in asymmetric C
-C
bonds forming cross-coupling reactions with α-amino radicals derived from N-aryl amino acids. A wide range of valuable enantiomerically pure β
- and β
-amino ketones were obtained in satisfactory yields with good-to-excellent enantioselectivities by using chiral phosphoric acid catalysts to control the stereochemistry and chemoselectivity. Fluoro-hetero-quaternary and full-carbon quaternary stereocenters that are challenging to prepare were successfully constructed.
Pyridine, one of the most important azaarenes, is ubiquitous in functional molecules. The electronic properties of pyridine have been exploited to trigger asymmetric transformations of prochiral ...species as a direct approach for accessing chiral pyridine derivatives. However, the full potential of this synthetic strategy for the construction of enantioenriched γ-functionalized pyridines remains untapped. Here, we describe the first enantioselective addition of prochiral radicals to vinylpyridines under cooperative photoredox and asymmetric catalysis mediated by visible light. The enantioselective reductive couplings of vinylpyridines with aldehydes, ketones, and imines were achieved by employing a chiral Brønsted acid to activate the reaction partners and provide stereocontrol via H-bonding interactions. Valuable chiral γ-secondary/tertiary hydroxyl- and amino-substituted pyridines were obtained in high yields with good to excellent enantioselectivities.
An enantioselective reduction of azaarene-based ketones through photoredox asymmetric catalysis is reported. With a transition metal-free dual catalytic system including a chiral phosphoric acid and ...a photosensitizer DPZ mediated by visible light, the transformations involved a tandem process involving double single-electron-transfer reductions and enantioselective protonation, providing valuable chiral alcohols in high yields (up to >99%) with good to excellent enantioselectivities (up to 97% ee).
Chiral hydrogen-bonding catalysis is a classic strategy in asymmetric organocatalysis, and it has been extensively used in a variety of fundamental chemical transformations. At the same time, visible ...light-driven photoredox catalysis is a powerful and sustainable tool commonly used in radical chemistry. The intriguing combination of these two catalysis platforms would open a new avenue for the direct and highly efficient synthesis of enantioenriched compounds. Inspired by the conceptual breakthrough of T. Bach, in recent years, significant progress has been made in cooperative photoredox and chiral hydrogen-bonding catalysis. By developing a variety of important types of reactions, a wide range of valuable chiral compounds have been successfully synthesized. In this review, the advances in this key area are systematically described, and the examples are organized according to the distinct bond-forming patterns in the construction of the stereocentres.
An efficient chemodivergent strategy for visible light photocatalysis is developed. In the presence of a dicyanopyrazine-derived chromophore (DPZ) photocatalyst, aerobic photooxygenation of indoles ...could produce either isatins or formylformanilides in satisfactory yields by judiciously selecting inorganic salts or modulating the reaction pH. The current chemodivergent method is also effective with 2-substituted indoles, opening straightforward synthetic routes to valuable 2,2-disubstituted 3-oxindoles, formylformanilide derivatives, and benzoxazinones. Mechanistic investigations involving cyclic voltammetry studies further confirm that reaction pH influences the electrochemical properties of DPZ, thus affecting the oxidative pathway by which indoles are being transformed.
A novel enantioselective protonation protocol that is triggered by reductive cross coupling of olefins is reported. When under cooperative photoredox and chiral hydrogen-bonding catalytic conditions ...and using a terminal reductant, various α-branched vinylketones with diverse vinylazaarenes could provide important enantioenriched azaarene derivatives containing tertiary stereocenters at their remote δ-position with high yields and enantioselectivities. This reaction system is also suitable for α-branched vinylazaarenes, thus successfully assembling elusive 1,4-stereocenters. The convenient late-stage modifications of products, especially the formation of remote ε-tertiary and ε-heteroquaternary carbon stereocenters, further highlight the important synthetic value of this method. Control experiments and density functional theory (DFT) calculations were conducted to elucidate the plausible reaction mechanism and origins of regioselectivity and stereoselectivity.
An enantioconvergent substitution of 3-substituted 3-chlorooxindoles with
N
-aryl glycines under visible light irradiation is reported. A transition-metal-free cooperative catalysis platform with a ...dicyanopyrazine-derived chromophore (DPZ) as a photoredox catalyst and a chiral Brønsted acid catalyst is effective for these transformations, which involve a single-electron transfer redox step and an enantioselective radical coupling. A variety of valuable chiral 3-aminomethylene-3-substituted oxindoles can be directly synthesized with high yields and enantioselectivities.
An enantioconvergent substitution of 3-substituted 3-chlorooxindoles with
N
-aryl glycines under visible light irradiation is reported.
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