The aryl‐to‐vinyl nickel 1,4‐migration (1,4‐Ni migration) reaction has been reported for the first time. The generated alkenyl Ni species undergo a reductive coupling reaction with unactivated ...brominated alkanes affording a series of trisubstituted olefins. This tandem reaction exhibits mild conditions, a broad substrate scope, high regioselectivity, and excellent Z/E stereoselectivity. A series of controlled experiments have shown that the critical 1,4‐Ni migration process is reversible. In addition, the alkenyl nickel intermediates obtained after migration are highly Z/E stereoselective and do not undergo Z/E isomerization. The obtained trace isomerization products are caused by the instability of the product.
The 1,4‐nickel migration process from aryl to alkenyl groups is now reported for the first time. The alkenyl nickel intermediates generated by this highly stereoselective migration process can be coupled with brominated alkanes to form multisubstituted olefins. The current method provides a new and efficient approach for the synthesis of Z/E olefins with high stereoselectivity.
An operationally simple radical difluoroalkylation/trifluoromethylation and alkynylation of unactivated alkenes under mild conditions has been developed. Through this protocol, a series of CF2/CF3‐ ...substituted linear alkynyl ketones were synthesized via a unique 1,2‐alkynyl radical migration. Notably, no transition‐ metal catalyst is needed in the developed reaction system, and excellent functional group compatibility was observed.
A novel copper(II) trifluoromethanesulfonate‐catalyzed intermolecular cascade annulation strategy for the construction of a great variety of pentacyclic compounds possessing valuable carbazole ...fragments was developed employing propargylic alcohols and (Z)‐2‐styryl‐1H‐indoles as the initial substrates. This protocol, which entails a sequential Meyer‐Schuster rearrangement/isomerization/‐cyclization cascade, enables facile and atom‐economical access to various pentacyclic compounds with broad functional‐group tolerance in good yields under mild conditions. The conversion could be efficiently scaled up to gram quantities, accentuating a potential application of this work.
An efficient palladium‐catalyzed cyclization and polyfluorophenylation of γ,δ‐unsaturated polyfluorobenzoyl oxime ester via iminopalladation/polyfluorobenzoyloxy decarboxylation cascade reaction is ...developed. The protocol provides a practical and atom‐economical access to a broad scope of various polyfluorophenylated dihydropyrrole derivatives. The reaction effectively utilizes the polyfluorobenzoyloxy leaving group as polyfluorophenylated source for the first time, precluding the need of additional polyfluoroarene. This is the first example of the introduction of electron‐deficient arenes in the further transformation of Narasaka‐Heck‐type reaction. Additionally, the reaction is conducted in a short time.
Heck Cyclization: An efficient palladium‐catalyzed cyclization and polyfluorophenylation of γ,δ‐unsaturated polyfluorobenzoyl oxime ester via iminopalladation/polyfluorobenzoyloxy decarboxylation cascade reaction is developed. The protocol provides a practical and atom‐economical access to a broad scope of various polyfluorophenylated dihydropyrrole derivatives. The reaction effectively utilizes the C6F5COO leaving group as C6F5 source for the first time, precluding the need of additional polyfluoroarene. Additionally, the reaction is conducted in a short time.
A novel and unprecedented intramolecular acyl transfer reaction via the palladium‐catalyzed insertion of isocyanide has been established. Isocyanides were inserted into C−O bond under mild ...conditions, using the readily available allyl ester as the starting materials. In addition, the intramolecular acyl transfer from the ester group oxygen atom to the isocyanide nitrogen atom afforded imide derivatives in moderate to excellent yields. Additionally, this transformation was validated as having operationally simple conditions and excellent functional group compatibility.
A copper-catalyzed radical cross-coupling of oxime esters and activated alkenes is accomplished for the synthesis of cyanoalkylsulfonylated oxindoles and cyanoalkyl amides via an aryl migration ...strategy. Specifically, the subsequent mechanism research indicates that the unique desulfonylation and sulfone addition processes were involved in the transformation. This transformation is identified as having good functional group applicability with two different quaternary stereocenter in a regioselective manner, which is controlled by the substituent group of the nitrogen.
A novel visible-light-induced palladium-catalyzed Heck reaction for bromine sugars and aryl olefins with high regio- and stereochemistry selectivity for the preparation of C-glycosyl styrene is ...described. This reaction takes place in one step at room temperature by using a simple and readily available starting material. This protocol can be scaled up to a wide range of glycosyl bromide donors and aryl olefin substrates. Mechanistic studies indicate that a radical addition pathway is involved.
Palladium-catalyzed C–H annulation reactions represent a compelling strategy to construct complex ring systems with high step economy. While there are many approaches to annulate structures by ...activation of a single C–H bond, transformations that proceed by activation of multiple C–H bonds are less explored. This is especially true for examples where one of the reacting C–H bonds is located at an sp3 center. However, exciting developments in palladium-catalyzed C–H activation continue to expand the scope of these transformations and provide innovative strategies to construct challenging carbon–carbon bonds. From these discoveries, sequential C–H activations have emerged as a powerful tool to access complex ring systems through the activation of C(sp2)–H/C(sp3)–H or C(sp3)–H/C(sp3)–H bonds. In this Perspective, we showcase recent examples that use this strategy in order to highlight the synthetic potential of C–H activation-enabled annulations and inspire future use of these disconnections for diverse scaffold synthesis.
The first synthesis of highly strained spirocyclobutane-pyrrolines via a palladium-catalyzed tandem Narasaka–Heck/C(sp3 or sp2)–H activation reaction is reported here. The key step in this ...transformation is the activation of a δ-C–H bond via an in situ generated σ-alkyl-Pd(II) species to form a five-membered spiro-palladacycle intermediate. The concerted metalation-deprotonation (CMD) process, rate-determining step, and energy barrier of the entire reaction were explored by density functional theory (DFT) calculations. Moreover, a series of control experiments was conducted to probe the rate-determining step and reversibility of the C(sp3)–H activation step.
A visible-light-induced glycoarylation of activated olefins has been accomplished. Glycosyl radicals are generated via radical transfer strategies between (TMS)3SiOH and glycosyl bromides. Subsequent ...radical translocation and rapid 1,4-aryl migration form β-sugar amide derivatives, and eight types of sugars are compatible with this reaction. Further, the cascade reaction produced a quaternary carbon center with good functional group adaptability and high regioselectivity in mild conditions.
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