Palladium‐Catalyzed Allylic Cycloaddition of Vinylethylene Carbonates with 3‐Nitrochromone

Chemo-, Regio- and Stereoselective Preparation of (Z)-2-Butene-1,4-Diol Monoesters via Pd-Catalyzed Decarboxylative Acyloxylation

(Z)-alkenes are useful synthons but thermodynamically less stable than their (E)-isomers and typically more difficult to prepare. The synthesis of 1,4-hetero-bifunctionalized (Z)-alkenes is particularly challenging due to the inherent regio- and stereoselectivity issues. Herein we demonstrate a general, chemoselective and direct synthesis of (Z)-2-butene-1,4-diol monoesters. The protocol operates within a Pd-catalyzed decarboxylative acyloxylation regime involving vinyl ethylene carbonates (VECs) and various carboxylic acids as the reaction partners under mild and operationally attractive conditions. The newly developed process allows access to a structurally diverse pool of (Z)-2-butene-1,4-diol monoesters in good yields and with excellent regio- and stereoselectivity. Various synthetic transformations of the obtained (Z)-2-butene-1,4-diol monoesters demonstrate how these synthons are of great use to rapidly diversify the portfolio of these formal desymmetrized (Z)-alkenes.

Recent advances in Pd-catalyzed asymmetric cyclization reactions

Over the past few decades, there have been major developments in transition metal-catalyzed asymmetric cyclization reactions, enabling the convenient access to a wide spectrum of structurally diverse chiral carbo- and hetero-cycles, common skeletons found in fine chemicals, natural products, pharmaceuticals, agrochemicals, and materials. In particular, a plethora of enantioselective cyclization reactions have been promoted by chiral palladium catalysts owing to their outstanding features. This review aims to collect the latest advancements in enantioselective palladium-catalyzed cyclization reactions over the past eleven years, and it is organized into thirteen sections depending on the different types of transformations involved.

Visible-light-enabled cascade cross-dehydrogenative-coupling/cyclization to construct α-chromone substituted α-amino acid derivatives

Organophotocatalytic cascade cross-dehydrogenative-coupling/cyclization reaction of o-hydroxyarylenaminones with α-amino acid derivatives for the construction of α-chromone substituted α-amino acid derivatives was developed. Various N-arylglycine esters, amides and dipeptides underwent the cascade cyclization reaction well with o-hydroxyarylenaminones to afford the corresponding 3-aminoalkyl chromones in good to excellent yields. This approach consists of visible-light-promoted oxidation of α-amino acid derivatives, the Mannich reaction, and intramolecular nucleophilic cyclization under acidic conditions, and features a wide reaction scope, a simple operation and mild reaction conditions, which may have the potential to be used for the synthesis of bioactive molecules.

Asymmetric cascades of the π-allyl complex: a journey from transition-metal catalysis to metallaphotocatalysis

The enantioselective catalytic cascade involving Tsuji-Trost allylation has provided a viable strategy for the construction of multiple asymmetric C-C and C-X centres and numerous methods have been developed around it for the synthesis of various vital scaffolds. The synthetic utility of this strategy was enhanced by replacing the customary allyl acetates with ethylene diacetates/dicarbonates, vinyl epoxides, vinyl oxetanes, vinyl ethylene carbonates, vinyl cyclopropanes, enynes, and dienes using transition-metal catalysis. One more milestone was achieved when metallaphotocatalysis provided the necessary platform for these cascades by using a cheaper metal. This review will provide a summary of these enantioselective catalytic cascades from 2015.

Rapid Construction of Tricyclic Furanobenzodihydropyrans by Asymmetric Tandem Reaction

A process based on the organocatalyzed Mannich/cycloketalization/transesterification tandem reaction of 1-(2-hydroxyaryl)-1,3-diketones and β,γ-alkynyl α-imino esters has been developed, delivering a variety of tricyclic furanobenzodihydropyrans with excellent results (up to 99% yield, 99% ee, and >19:1 dr).

Stereoselective Total Synthesis of Formosanol, Tsugacetal, and Methyl β-Conidendral

The first enantioselective total synthesis of aryltetralin lignan acetals, (-)-formosanol, (+)-tsugacetal, (+)-methyl β-conidendral, and their enantiomers have been accomplished on the basis of the Pd-catalyzed asymmetric allylic cycloaddition as a key step. Six stereoisomers of the lignan acetals have been synthesized via a 7-8 step sequence in up to 14% overall yield. The in vitro cytotoxicity against several cancer cells has preliminarily been examined for the obtained six stereoisomers of lignan acetals.

Route to Chiral Tetrahydrofuran Acetals via Pd-Catalyzed Asymmetric Allylic Cycloaddition of Vinyl Epoxides with β-Keto Enol Ethers

An efficient method for the synthesis of functionalized chiral tetrahydrofuran (THF) acetals via Pd-catalyzed asymmetric allylic cycloaddition has been developed. With a palladium catalyst coordinated by a chiral phosphine ligand, the protocol is enabled to combine readily available vinyl epoxides and β-keto enol ethers to produce THF acetals bearing three stereocenters in a broad substrate scope with uniformly high levels of enantio- and diastereoselectivity.

Pd-Catalyzed regio- and stereoselective allylic substitution of vinylethylene carbonates with 1,2,4-triazoles

N ¹-Substituted 1,2,4-triazoles are ubiquitous skeletons in medicinal agents, agrochemicals, and organic materials. Herein, an efficient and practical method for the synthesis of N¹-allylated 1,2,4-triazoles via Pd-catalyzed allylic substitution of vinylethylene carbonates (VECs) with 1,2,4-triazoles has been developed. By using a catalyst generated in situ from Pd₂(dba)₃·CHCl₃ and DPPE under mild conditions, the process allows rapid access to N¹-allylated 1,2,4-triazoles bearing diverse functionalities in high yields with excellent N¹-selectivities, linear-selectivities, and Z-stereoselectivities.

Pd-Catalyzed Asymmetric Three-Component Allenol Carbopalladation and Allylic Cycloaddition Cascade: A Route to Functionalized Tetrahydrofurans

The first Pd-catalyzed asymmetric three-component reaction of 2,3-allenol, aryl iodides, and 2-arylmethylenemolononitriles has been developed via an allenol carbopalladation and an allylic cycloaddition cascade. This process allows rapid access to substituted tetrahydrofurans bearing diverse functional groups in good yields with high diastereoselectivities and excellent enantioselectivities. The concise total synthesis of a lignan, (-)-2-episesaminone, has been achieved by the elaboration of a functionalized tetrahydrofuran obtained from this reaction.

Palladium-catalysed stereoselective [3 + 2] annulation of vinylethylene carbonates and tryptanthrin-based ketones

The first example of palladium-catalysed [3 + 2] annulation of VECs and ketones has been developed, allowing the efficient synthesis of indoloquinazolinones in generally excellent yields with good stereoselectivity.

Recent advances of chromone-based reactants in the catalytic asymmetric domino annulation reaction

Chiral polycyclic chromanones are important heterocyclic frameworks that constitute the core structures of many natural products and bioactive molecules.