Palladium-catalyzed Cascade Research Articles

Palladium-Catalyzed Cascade Cyclization of Alkene-Tethered Aryl Halides with o-Bromobenzoic Acids: Access to Diverse Fused Indolo[2,1-a]isoquinolines.

A novel palladium-catalyzed cascade cyclization of alkene-tethered aryl halides with o-bromobenzoic acids is described, which provides an efficient avenue for building various fused hexacyclic scaffolds containing indolo[2,1-a]isoquinoline in moderate to excellent yield. The method enables the construction of three C-C bonds through an intramolecular carbopalladation, C-H activation, and a decarboxylation sequence. Furthermore, dihydrocyclohepta[de]naphthalene-fused indolo[2,1-a]isoquinolines can be synthesized in moderate yield by constructing a seven-membered ring.

Palladium-Catalyzed Cascade Annulation/Allylation of Alkynyl Oxime Ethers with Allyl Halides: Rapid Access to Fully Substituted Isoxazoles.

A novel and efficient approach for the synthesis of functionalized isoxazoles via palladium-catalyzed cascade annulation/allylation of alkynyl oxime ethers with allyl halides has been established. The present protocol exhibits mild reaction conditions, good functional group compatibility, and convenient operation. Moreover, scalability was performed and further decoration of the isoxazole product was achieved.

Palladium-Catalyzed Cascade Reaction of o-Cyanobiaryls with Arylboronic Acids: Synthesis of 5-Arylidene-7-aryl-5H-dibenzo[c,e]azepines.

A palladium-catalyzed cascade reaction of 2'-acetyl-[1,1'-biphenyl]-2-carbonitriles with arylboronic acids is developed. This reaction affords a new class of seven-membered 5-arylidene-7-aryl-5H-dibenzo[c,e]azepines with good functional group compatibility and selectivity. Reaction mechanistic study suggests that this transformation involves carbopalladation of nitrile and subsequent intramolecular cyclization followed by oxidative Heck coupling.

Palladium-Catalyzed Cascade Intramolecular Cyclization and Allylation of Enynoates with Allylic Alcohols.

A Pd(II)-catalyzed mild and highly regioselective 6- endo cyclization/allylation reaction of enynoates with simple allylic alcohols has been developed. Under mild reaction conditions, the vinyl palladium species generated in situ after cyclization could insert C-C double bond of allylic alcohol through cross-coupling reaction and lead to the formation of allyl pyrone via β-OH elimination. This cascade cross-coupling reaction represents a direct and atom economic methodology for the construction of novel allyl pyrones in moderate to good yields.

Palladium-Catalyzed Stereospecific Oxidative Cascade Reaction of Allenes for the Construction of Pyrrole Rings: Control of Reactivity and Selectivity

A palladium-catalyzed oxidative cascade reaction of α-tosylamide allenes has been developed. The reactivity of the allenes is controlled by the tosylamide group. In the presence of terminal alkynes...

Rapid Construction of Fused Heteropolycyclic Aromatics via Palladium-Catalyzed Domino Arylations of Imidazopyridine Derivatives.

By using diaryliodonium salts, a novel approach of a palladium-catalyzed cascade of diarylation/intramolecular dehydrogenative coupling reaction has been developed in the synthesis of phenanthro-imidazopyridine fused heteropolycycles. The method can tolerate various substrates, and the target products were rapidly constructed in one pot. Furthermore, studies of the detailed reaction mechanism provide an insight into the C-H functionalization of 2-aryl-imidazopyridine derivatives and the C-C bond formations in the presence of palladium catalyst.

Stereoselective Pd-Catalyzed Decarboxylative Allylation: Assembly of Highly Functionalized Allylic Amines Bearing a Quaternary Center.

Here, we report a practical and reliable methodology to direct construction of tri- and tetrasubstituted olefins bearing an allylic amine, with the concomitant construction of the sterically congested quaternary stereocenter through stereoselective palladium-catalyzed cascade decarboxylation of vinyloxazolidinones.

Palladium-Catalyzed Cascade Cyclization/Bromination of 2-Alkynone O-Methyl Oximes in Ionic Liquid

Palladium-Catalyzed Cascade Cyclization/Bromination of 2-Alkynone <i>O</i>-Methyl Oximes in Ionic Liquid

A palladium-catalyzed three-component cascade S-transfer reaction in ionic liquids

A palladium-catalyzed three component cascade S-transfer reaction for the assembly of functionalized 4-sulfenylisoxazoles in ionic liquids was described.

Synthesis of the core structure of phalarine.

The core skeleton of phalarine was rapidly synthesised through novel palladium-catalysed dearomative spirocyclisation and a palladium-catalysed Wacker-carbonylative cyclisation cascade. The two key steps allowed for the efficient construction of a tricyclic propeller skeleton bearing contiguous tetrasubstituted carbon centres, within 3 steps from a topologically planar precursor.

A palladium-catalyzed multi-component annulation approach towards the synthesis of phenanthrenes.

An efficient palladium-catalyzed three-component cascade reaction has been developed for the facile construction of phenanthrene frameworks. The transformation is driven by a controlled reaction sequence of Suzuki-Miyaura coupling followed by the insertion of alkynes, and finally, annulation to yield phenanthrene derivatives via C-H activation. This methodology is able to accommodate a variety of substrates and affords the anticipated products in good to excellent yields.

Synthesis of bicyclic ethers by a palladium-catalyzed oxidative cyclization-redox relay-π-allyl-Pd cyclization cascade reaction.

Bicyclic ether scaffolds are found in a variety of natural products and are of interest in probe and drug discovery. A palladium-catalyzed cascade reaction has been developed to provide efficient access to these scaffolds from readily available linear diene-diol substrates. A Pd redox-relay process is used strategically to transmit reactivity between an initial oxypalladative cyclization and a subsequent π-allyl-Pd cyclization at remote sites. The reaction affords a variety of bicyclic ether scaffolds with complete diastereoselectivity for cis-ring fusion.

Direct access to substituted benzo[b]carbazoles through cascade annulation of 2-vinylbenzaldehydes with indoles.

A highly efficient palladium-catalyzed cascade annulation of 2-vinylbenzaldehydes with indoles has been achieved to afford 6-(3-indolyl)benzo[b]carbazoles under mild conditions in good yield and with excellent regioselectivity. Mechanistic investigations reveal that the reaction proceeds via double addition of indoles, unexpected intramolecular 1,4-aryl and 1,2-hydrogen migrations, and oxidative aromatization.

A visible-light-induced cascade reaction of etherification/C-C cyclization: efficient synthesis of dibenzo[b,d]oxepin-7(6H)-ones.

A visible-light-induced palladium-catalyzed cascade reaction was developed by etherification/C-C coupling cyclization of α-bromoacetophenones with phenols. A series of dibenzo[b,d]oxepin-7(6H)-one derivatives were efficiently synthesized by using this method in good yields. Furthermore, this method was applied to the synthesis of protosappanin A. The protocol has advantages such as simple reaction conditions, wide range of substrates and high reaction efficiency.

Palladium-catalyzed cascade reactions of alkene-tethered carbamoyl chlorides with N-tosyl hydrazones: synthesis of alkene-functionalized oxindoles.

A palladium-catalyzed cascade reaction of alkene-tethered carbamoyl chlorides with N-tosyl hydrazones is described. It provided a new way to synthesize various alkene-functionalized oxindoles bearing an all-carbon quaternary center. The olefin moieties could serve as versatile handles for further elaboration. This transformation was highly efficient and showed good functional group tolerance.

Construction of Quaternary Stereocenters by Palladium-Catalyzed Carbopalladation-Initiated Cascade Reactions.

The enantioselective synthesis of molecules containing quaternary stereocenters is a field of intense research interest and development. Among the known organic transformations, carbopalladation-initiated domino transformations constitutes a general method for the construction of compounds containing cyclic or spiro quaternary stereocenters. In this Minireview, recent achievements in palladium-catalyzed domino Heck/C-H functionalizations and developments in enantioselective carbopalladation-initiated domino processes are summarized.

Palladium-Catalyzed Cascade Carbopalladation/Phenol Dearomatization Reaction: Construction of Diversely Functionalized Spirocarbocyclic Scaffolds.

A novel palladium-catalyzed cascade carbopalladation/phenol dearomatization reaction has been achieved. The process provides a variety of indolone-, dihydrobenzofuran-, dihydrobenzopyran- and hydroquinoline-containing spirofused molecules bearing two quaternary centers in moderate to good yields. The potential synthetic utility of this method is demonstrated by a gram-scale experiment and further transformations.

Palladium/Norbornene Chemistry: Synthesis of Norbornene-Containing Arylsilanes Involving Double C-Si Bond Formation.

A novel palladium-catalyzed three-component cascade reaction of aryl halides with norbornene and hexamethyldisilane has been described, which allows the simultaneous construction of two C-Si bonds and one C-C bond. The method achieves ortho C-H functionalization of aryl halides through the formation of the five-membered palladacycle, leading to norbornene-containing arylsilanes.

Palladium-Catalyzed Cascade Difluoroalkylation/Cyclization of N-Propargylamides: Synthesis of Oxazoles and Oxazolines.

A palladium-catalyzed process to construct oxazoles and oxazolines with broad functional-group tolerance has been developed, and the method introduces difluoromethyl groups into heterocycles in a one-pot fashion. This system uses a carbonyl oxygen as the acceptor for the addition of a vinylpalladium intermediate to achieve the cyclization. Oxazoline derivatives are generated as the Z-isomer with high stereoselectivity. Additionally, we validated the tentative mechanism of this reaction.

Palladium-Catalyzed Selective Five-Fold Cascade Arylation of the 12-Vertex Monocarborane Anion by B-H Activation.

A series of cage penta-arylated carboranes have been synthesized by palladium-catalyzed intermolecular coupling of the C-carboxylic acid of the monocarba- closo-dodecaborate anion [CB11H12]- with iodoarenes by direct cage B-H bond functionalization. These transformations set a record in terms of one-pot directing group-mediated activation of inert bonds in a single molecule. The methodology is characterized by high yields, good functional group tolerance, and complete cage regioselectivity. The directing group COOH can be easily removed during or after the intermolecular coupling reaction. The mechanistic pathways were probed using density functional theory calculations. A Pd(II)-Pd(IV)-Pd(II) catalytic cycle is proposed, in which initial coupling is followed by preferred B-H activation of the adjacent boron vertex, and continuation of this selectivity results in a continuous walking process of the palladium center. The methodology opens a new avenue toward building blocks with 5-fold symmetry.