C-H functionalization has been emerging as a powerful method to establish carbon-carbon and carbon-heteroatom bonds. Many efforts have been devoted to transition-metal-catalyzed direct ...transformations of C-H bonds. Metal carbenes generated
in situ
from transition-metal compounds and diazo or its equivalents are usually applied as the transient reactive intermediates to furnish a catalytic cycle for new C-C and C-X bond formation. Using this strategy compounds from unactivated simple alkanes to complex molecules can be further functionalized or transformed to multi-functionalized compounds. In this area, transition-metal-catalyzed carbene insertion to C-H bonds has been paid continuous attention. Diverse catalyst design strategies, synthetic methods, and potential applications have been developed. This critical review will summarize the advance in transition-metal-catalyzed carbene insertion to C-H bonds dated up to July 2021, by the categories of C-H bonds from aliphatic C(sp
3
)-H, aryl (aromatic) C(sp
2
)-H, heteroaryl (heteroaromatic) C(sp
2
)-H bonds, alkenyl C(sp
2
)-H, and alkynyl C(sp)-H, as well as asymmetric carbene insertion to C-H bonds, and more coverage will be given to the recent work. Due to the rapid development of the C-H functionalization area, future directions in this topic are also discussed. This review will give the authors an overview of carbene insertion chemistry in C-H functionalization with focus on the catalytic systems and synthetic applications in C-C bond formation.
This review summarizes the recent advance in transition-metal-catalyzed carbene insertion to C-H bonds, forming diverse C-C bonds.
Carbon-sulfur bond cross-coupling has become more and more attractive as an alternative protocol to establish carbon-carbon and carbon-heteroatom bonds. Diverse transformations through ...transition-metal-catalyzed C-S bond activation and cleavage have recently been developed. This review summarizes the advances in transition-metal-catalyzed cross-coupling
via
carbon-sulfur bond activation and cleavage since late 2012 as an update of the critical review on the same topic published in early 2013 (
Chem. Soc. Rev.
, 2013,
42
, 599-621), which is presented by the categories of organosulfur compounds, that is, thioesters, thioethers including heteroaryl, aryl, vinyl, alkyl, and alkynyl sulfides, ketene dithioacetals, sulfoxides including DMSO, sulfones, sulfonyl chlorides, sulfinates, thiocyanates, sulfonium salts, sulfonyl hydrazides, sulfonates, thiophene-based compounds, and C&z.dbd;S functionality-bearing compounds such as thioureas, thioamides, and carbon disulfide, as well as the mechanistic insights. An overview of C-S bond cleavage reactions with stoichiometric transition-metal reagents is briefly given. Theoretical studies on the reactivity of carbon-sulfur bonds by DFT calculations are also discussed.
This review summarizes the advances in transition-metal-catalyzed cross-coupling
via
carbon-sulfur bond activation and cleavage since late 2012 as an update of the critical review published in early 2013 (
Chem. Soc. Rev.
, 2013,
42
, 599-621).
An examination of the asymmetric hydrogenation of arenes and heteroarenes is presented. A look at the use of asymmetric hydrogenation of quinolines is also presented.
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The enantioselective α‐addition of deconjugated butenolides has rarely been exploited, in contrast to the well‐studied γ‐addition of deconjugated butenolides. In this study, an unprecedented ...asymmetric α‐addition/transesterification of deconjugated butenolides with ortho‐quinone methides generated in situ afforded a series of functionalized 3,4‐dihydrocoumarins containing two contiguous stereogenic centers with excellent diastereo‐ and enantioselectivity. DFT calculations suggested that the rarely observed regioselectivity was due to the distortion energy that resulted from the interaction between the nucleophilic dienolate and the electrophilic ortho‐quinone methide.
The alpha… but not the gamma: The α‐addition of deconjugated butenolides has rarely been exploited, in contrast to their well‐studied γ‐addition. Now an unprecedented asymmetric α‐addition/transesterification of deconjugated butenolides with ortho‐quinone methides generated in situ from 2‐(1‐tosylalkyl)phenols has been developed for the synthesis of functionalized 3,4‐dihydrocoumarins containing two contiguous stereogenic centers (see scheme).
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An ultra-high voltage viologen/Br2 flow battery was designed based on a novel two-electron viologen derivative, a highly-conductive and low-cost porous polyolefin membrane, and an effective ...complexing agent, making the battery one of the most stable two-electron viologen-based flow batteries with superior energy and power density at the same time.
Concise construction of furan and thiophene units has played an important role in the synthesis of potentially bioactive compounds and functional materials. Herein, an efficient Lewis acid ZnCl2 ...catalyzed 4+1 annulation of alkylthio‐substituted enaminones is reported, that is, α‐oxo ketene N,S‐acetals with sulfur ylides to afford 2‐acyl‐3‐aminofuran derivatives. In a similar fashion, 4+1 annulation of the corresponding enaminothiones, that is, α‐thioxo ketene N,S‐acetals, with sulfur ylides efficiently proceeded to give multisubstituted 3‐aminothiophenes. This method features wide substrate scopes as well as broad functional group tolerance, offering a concise route to highly functionalized furans and thiophenes.
An efficient Lewis acid catalyzed protocol has been developed for the synthesis of 2‐acyl‐3‐amino‐substituted furan and thiophene derivatives from enaminones and enaminothiones. The 4+1 annulation allows for broad substrate scopes, high efficiency, and good functional‐group tolerance.
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Rhodium(III)-catalyzed annulative coupling of sulfoxonium ylides with allenoates was achieved, forming highly functionalized cyclopropanes with a quaternary carbon center by means of the sulfoxonium ...ylide functionality as a traceless bifunctional directing group and C4 synthon via an arene C–H activation and cyclopropanation cascade. The protocol features simultaneous formation of three new C–C bonds in one pot with excellent diastereoselectivity. The resultant cyclopropanation products could be further transformed to diverse synthetically useful compounds.
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With the rapid development of biomimetic asymmetric reduction, the demand for efficient chiral and regenerable NAD(P)H models is growing rapidly. Herein, a new class of 2.2paracyclophane-based chiral ...and regenerable NAD(P)H models (CYNAMs) was designed and synthesized. The first enantioselective biomimetic reduction of tetrasubstituted alkene flavonoids has been successfully realized through enzyme-like cooperative bifunctional activation, giving chiral flavanones with up to 99% yield and 99% ee.
With the rapid development of biomimetic asymmetric reduction, the demand for efficient chiral and regenerable NAD(P)H models is growing rapidly.
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The development of biomimetic chemistry based on the NAD(P)H with hydrogen gas as terminal reductant is a long‐standing challenge. Through rational design of the chiral and regenerable NAD(P)H ...analogues based on planar‐chiral ferrocene, a biomimetic asymmetric reduction has been realized using bench‐stable Lewis acids as transfer catalysts. A broad set of alkenes and imines could be reduced with up to 98 % yield and 98 % ee, likely enabled by enzyme‐like cooperative bifunctional activation. This reaction represents the first general biomimetic asymmetric reduction (BMAR) process enabled by chiral and regenerable NAD(P)H analogues. This concept demonstrates catalytic utility of a chiral coenzyme NAD(P)H in asymmetric catalysis.
Through rational design of chiral and regenerable NAD(P)H analogues based on planar‐chiral ferrocene, a biomimetic asymmetric reduction has been realized using bench‐stable Lewis acids as transfer catalysts. A broad set of tetrasubstituted alkenes and imines could be reduced with up to 98 % yield and 98 % ee. This protocol represents the first general biomimetic asymmetric reduction process enabled by NAD(P)H analogues.
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The enantioselective conjugated addition of tritylthiol to in situ generated ortho‐quinone methides (o‐QMs) is catalyzed by an acid–base bifunctional squaramide organocatalyst. The transformation ...proceeds with high yield (up to 99 %) and stereoselectivity (up to 97:3 e.r.) using water as solvent under mild conditions. The catalyst system provides a new strategy for the synthesis of optically active benzyl mercaptans. Control experiments suggested that o‐QMs are generated by the tertiary amine moiety of the squaramide organocatalyst and that the water–oil biphase is crucial for achieving high reactivity and stereoselectivity.
Phased out: A squaramide organocatalyst mediates the asymmetric synthesis of α‐aryl‐ and α‐alkyl‐substituted benzyl mercaptans through the thiolation of in situ generated ortho‐quinone methides at a water–oil interface. The reactions exhibit wide substrate scope and excellent enantioselectivity because of the spatial separation of the inorganic base in the aqueous phase from the chiral components in the organic phase.
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![ZnCl2‐Catalyzed [4+1] Annul...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0947-6539/small "ZnCl2‐Catalyzed [4+1] Annulation of Alkylthio‐Substituted Enaminones and Enaminothiones with Sulfur Ylides")
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