Search

Comprehensive Summary: A copper‐catalyzed cyanation/diarylmethylation of formamides has been developed for the synthesis of α‐cyano functionalized tetra‐substituted olefins by utilizing para‐quinone methides (p‐QMs) and trimethylcyanosilane as functionalization sources. Various kinds of p‐QMs and formamides are well tolerated, delivering the desired products with 72%—94% yields, demonstrating broad functional group tolerance. Notably, the reaction does not require noble metals and proceeds regioselectively under mild conditions. Based on step‐by‐step control experiments, Hammett studies and DFT calculation, a plausible mechanism is proposed. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: The difunctionalization of bicyclo[1.1.0]butanes is an under‐explored transformation that accesses to moieties that are otherwise difficult to prepare. Herein, a new oxidative radical alkylarylation of N‐aryl bicyclobutyl amides with C(sp3)−H feedstocks is achieved in an atom‐economic and photocatalyst‐ and light‐free manner. This protocol follows a sequential C(sp3)–H/C(sp2)–H functionalization, providing an efficient route for diversity‐oriented synthesis of functionalized 3‐spirocyclobutyl oxindoles. In particular, a wide range of C(sp3)−H feedstocks, including ether, alcohol, amine, thioether, polychlorinated methane, silane, acetone, acetonitrile, toluene, and alkane are all suitable for the C(sp3)−H functionalization, demonstrating the broad applicability of this transformation. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A novel visible‐light‐induced radical cascade 6‐endo cyclization of dienes (N‐(2‐vinylphenyl)acryl amides) is developed utilizing α‐carbonyl bromides as alkyl reagents. This approach affords an efficient way for synthesizing six‐membered benzo‐fused lactam derivatives with chemo‐ and regio‐selectivity and good functional group tolerance. Primary, secondary, and tertiary bromides are well‐compatible with this cascade cyclization reaction. [ABSTRACT FROM AUTHOR]

A direct visible‐light‐promoted radical‐triggered tandem cyclization of 1,7‐diene systems with cyclic sulfonium salts by using copper(I)‐based complexes as photoredox catalyst is developed. With this approach, a variety of sulfur‐containing polycyclic derivatives are prepared through alkylation/6‐exo‐trig cyclization/5‐exo‐trig cyclization of 1,7‐diene systems under mild conditions. In addition, the photoinduced copper‐catalyzed ring‐opening of cyclic sulfonium salts provides the alkyl radical intermediates, which prefers addition to the C−C double bond that connected to the aromatic ring rather than the electron‐deficient vinyl in 1,7‐dienes. Moreover, oxidation of the desired sulfur‐containing polycyclic products provides a strategy for the preparation of remote nitrogen‐fused polycyclic substituted sulfoxide or sulfone‐containing derivatives. [ABSTRACT FROM AUTHOR]

A four‐component reaction of N‐arylpropiolamides, Hantzsch esters, Na2S2O5 and water via a radical cascade cyclization process with the insertion of sulfur dioxide mediated by K2S2O8 is reported. A series of alkylsulfonated spiro[4,5] trienones are prepared up to 86% yield with a good functional group tolerance and substrate applicability. Preliminary mechanism experiments indicate that carbonyl oxygen of spiro[4,5] trienones originated from water. [ABSTRACT FROM AUTHOR]

A novel strategy of visible‐light photoredox catalysis ipso‐annulation of activated alkynes with polychloroalkanes for the synthesis of 3‐polychloroalkyl spiro[4,5]trienones, which used 4‐methoxybenzenediazonium tetrafluoroborate salt as a hydrogen atom transfer reagent, is described. This polychloroalkylation/ spirocyclization of alkynes offers a widely range of 3‐polychloroalkyl‐spiro[4,5]trienone derivatives in high yields with a broad substrate scope via selective C(sp3)‐H homolytic cleavage. The results of controlled experiments showed that this method involves a radical process. The polyhaloalkyl radical species generated from intermolecular hydrogen atom transfer (HAT) between aryl radical and polychloroalkanes. [ABSTRACT FROM AUTHOR]

A simple and efficient oxidative‐promoted radical cascade annulation of ynone derivatives with ketones for the construction of a series of oxoalkyl‐substituted indenones in moderate to good yields is described. The control experiment results indicate that the oxidative acetmethylation/arylation of ynone derivatives involves a radical cascade cyclization process. This is an operationally simple and efficient protocol which will be attractive in organic synthesis chemistry. [ABSTRACT FROM AUTHOR]

An oxidative sulfonylation/cyclisation of N‐propargylindoles with Hantzsch esters through sulfur dioxide insertion has been developed. The method uses Na2S2O5 as sulfur dioxide source along with 4‐alkyl‐substituted Hantzsch esters as radical precursors for accessing sulfonyl radicals, and allows for the synthesis of 2‐sulfonated 9H‐pyrrolo[1,2‐a]indoles. [ABSTRACT FROM AUTHOR]

A mild and efficient Zn(II)‐catalyzed regioselective 1,6‐hydroarylation of para‐quinone methides (p‐QMs) with electron‐rich arenes protocol is reported. A variety of electron‐rich arenes and para‐quinone methides are well tolerated under mild conditions, delivering a broad range of triarylmethanes in good to excellent yields. The present method also works well for the hydroarylation of p‐QMs with other nucleophiles, such as aniline, indole and phenol derivatives, offering the corresponding triarylmethanes with good yields under the standard conditions. The possible mechanism for the formation of C(sp3)−C(sp2) bonds in hydroarylation reactions has been explored by step‐by‐step control experiments, and the reaction may follow a second‐order manner in a chemical kinetic study. [ABSTRACT FROM AUTHOR]

The visible‐light‐induced synthesis of 5‐phosphoryl‐functionalized pyrroles has been established by eosin Y catalysis, and different electron‐donating or electron‐withdrawing group substituted secondary H‐phosphine oxides and phenacylmalononitriles showed good reactivity toward the reaction, affording the cascade phosphinoylation/cyclization products in 82–98% yields via P−C/C−N annulation. Step‐by‐step control experiments and 31P NMR tracking experiments were further performed to gain the insights of the plausible reaction mechanism and kinetic reaction process. This reaction may have implications for the construction of C(sp2)−P bonds in organophosphorus chemistry. [ABSTRACT FROM AUTHOR]

A new photoinduced acylation/arylation of N‐(arylsulfonyl)acrylamide with acyl oxime esters through a nitrogen‐centered radical protocol has been disclosed for efficient preparation of functionalized indolin‐2‐ones, which proceeds through a cascade acyl radical addition of carbon‐carbon double bond, aryl migration, desulfonylation, and intramolecular cyclization sequence. This redox‐neutral strategy features excellent selectivity, good substituent tolerance, and wide substrate scope. [ABSTRACT FROM AUTHOR]

A facile and efficient method for the synthesis of α‐diarylmethyl substituted phenols from para‐quinone methides (p‐QMs) with phenols has been developed by using phosphoric acid as the catalyst and water as the green solvent under mild conditions. In addition, when TEMPO was added as an additive for the reaction, the diaryl‐substituted para‐quinone methides could be generated as the target product. The reactions show high functional group tolerance, good to excellent yields and unique selectivity, and a broad range of α‐diarylmethyl motif containing phenol(s) and quinones could be prepared through the divergent methods. Furthermore, a series of control experiments were performed to gain the insights of the plausible mechanisms. These protocols have a high atomic economy, and may have significant implications for the construction of C(sp3)−C(sp2) bonds in organic synthesis. [ABSTRACT FROM AUTHOR]

An efficient, cheap and green protocol for the highly regioselective 1,6‐hydroarylation of para‐quinone methides (p‐QMs) with indoles at the C‐3 position has been established by phosphoric acid catalysis in water under transition‐metal‐free reaction conditions. A wide range of indole derivatives and para‐quinone methides (p‐QMs) are compatible for the reaction, affording the corresponding 1,6‐hydroarylation products with good to excellent yields. The possible mechanism of the reaction has been explored through step‐by‐step control experiments. The protocol is convenient for practical applications, leading to a safe, green and feasible way for the formation of C‐3 diarylmethyl functionalized indole derivatives. [ABSTRACT FROM AUTHOR]

A nitrogen‐centered radical strategy for the preparation of 3‐acylated spiro[4,5]trienones via visible‐light‐mediated acylation/ipso‐cyclization of alkynes with acyl oxime esters is reported. The alkyl‐ and aryl‐substituted acyl radicals, which generate from the cleavage of carbon‐carbon σ‐bonds in acyl oxime esters via nitrogen‐centered radical pathway, attack the carbon‐carbon triple bonds in propiolamides and then undergo ipso‐cyclization. This method provides a way for the construction of 3‐acyl‐substituted spiro[4,5]trienones, which can introduce aryl‐ or alkyl‐substituted acyl into spiro[4,5]trienone skeletons. [ABSTRACT FROM AUTHOR]

A simple and efficient method for the regioselective iodophosphoryloxylation of alkenes with P(O)−OH bonds has been established by using NIS (N‐iodosuccinimide) as the iodination reagent under transition‐metal‐free conditions. The present protocol is compatible with different functional groups, and suitable for various alkenes and P(O)−OH compounds. A variety of functionalized β‐iodo‐1‐ethyl phosphinic/phosphoric acid esters are obtained in good to excellent yields, which could be further transformed to diversified building blocks for the synthesis of bioactive compounds, pharmaceuticals and functional materials. [ABSTRACT FROM AUTHOR]

Iron‐mediated radical cyanoalkylsulfonylation/arylation of active olefins with cycloketone oxime derivatives via cleavage of C−C single bond and insertion of SO2 is developed for the preparation of cyanoalkylsulfonylated oxindoles. This difunctionalization of carbon−carbon double bond via a radical pathway involves cyclobutanone oxime ester fragmentation, sulfonyl radical generation and radical addition/5‐exo cyclization. The methodology displays good functional group tolerance and does not require any external bases or oxidants. [ABSTRACT FROM AUTHOR]

A copper‐catalyzed diphenylation of P(O)−OH bonds with cyclic diaryliodonium salts is described. Valuable 2′‐iodo substituted biaryl phosphinic/phosphoric acid esters were obtained in good to excellent yields, which could be further transformed to diversified building blocks for the synthesis of bioactive compounds, pharmaceuticals and functional materials. [ABSTRACT FROM AUTHOR]

A versatile base‐catalyzed method for the 1,6‐conjugated addition/aromatization of para‐quinone methides with P(O)–H compounds is illustrated. Further studies on this reaction by using optically active H‐phosphinates show that the reaction takes place stereospecifically with retention or inversion of configuration at the phosphorus center. It is a simple way to produce a broad spectrum of functionalized phosphane oxides and phosphinates from basic P(O)–H starting materials. This finding also contributes significantly to the stereosynthesis in the catalysis. [ABSTRACT FROM AUTHOR]

Without using any transitionmetal and base, an eco‐friendly, practical and economical protocol has been established for the one‐pot synthesis of diverse (E)‐1‐phenyl‐4‐sulfonylbut‐1‐enes from easily accessible starting materials. This strategy features a wide substrate scope, tolerates a broad range of functional groups, employs a less expensive oxidant, is operationally simple, and can be easily scaled‐up. [ABSTRACT FROM AUTHOR]

Asymmetric esterification of racemic mandelic acid (MA) was conducted in 1,2-dichloroethane using lipase Novozym 435 as catalyst. Different alcohols were screened for esterification to achieve high conversion and enantioselectivity. The results show that ethanol is the best alcohol substrate among tested alcohols, and long-chain alcohols show lower enantioselectivities. The effect of substrate concentrations on esterification with ethanol was studied, and the result indicates an alcohol inhibition. To examine the mechanism of the alcohol chain length effect, the ping-pong bi-bi mechanism with competitive alcohol inhibition was applied to build a model. By comparing the kinetic parameters of methanol, ethanol, butanol, heptanol, and octanol, it was found that both the Michaelis constant and the inhibition constant of alcohol increase with the increase in alcohol chain length, indicating that the balance between nucleophilicity and the inhibition effect is the possible reason for the highest conversion and enantioselectivity as shown by ethanol. [ABSTRACT FROM AUTHOR]