Palladium-Catalyzed Regioselective and Stereoselective Oxidative Heck Arylation of Allylamines with Arylboronic Acids

Rh(III)-Catalyzed Diastereo- and Enantioselective Regiodivergent (Hetero)Arylamidation of (Homo)Allylic Sulfides

A rhodium-catalyzed 3-component conjunctive diastereo- and regioselective arylamidation of (homo)allylic sulfides, organon boronic acids, and dioxazolones is reported. These reactions deliver the 1,2-insertion and 2,1-insertion arylamidation products, respectively, for allylic sulfides and homoallylic sulfides. The enantioselective arylamidation of terminal and internal allylic sulfides is achieved, furnishing various 1,3-N,S compounds featuring one or two contiguous stereocenters in high yields and with high diastereo- and enantioselectivities. Mechanistic studies suggest a change in the turnover-limiting and selectivity-determining steps induced by the native and easily removable sulfide group.

DMSO-promoted direct δ-selective arylation of p-quinone methenylpiperidine bearinides to generate fuchsones under metal-free conditions by employing p-QMs themselves or substituted phenols as aryl sources

Fuchsones have wide applications in modern society. Present methods for generating fuchsones have many disadvantages and there are significant limitations for further exploration of fuchsone applications. Herein, we describe a DMSO-promoted direct δ-selective arylation of p-QMs to synthesize symmetrical and unsymmetrical fuchsones under metal-free conditions by employing p-QMs themselves or substituted phenols as aryl sources. As unprecedented methods, these novel strategies present a great advantage and significance for further exploration of fuchsones and the development of new applications.

Pd-Catalyzed desulfitative arylation of olefins by N-methoxysulfonamide

A novel Pd-catalyzed protocol for the desulfitative Heck-type reaction of N-methoxy aryl sulfonamides with alkenes was reported. The cross-coupling reaction was performed successfully with a variety of olefins to obtain aryl alkenes. Different substituents on the aromatic ring of N-methoxysulfonamides were also found to be compatible with the reaction conditions. Expectedly, the reaction proceeds through CuCl₂-promoted generation of the nitrogen radical and subsequent desulfonylation under thermal conditions to afford the aryl radical for the Pd-catalyzed coupling reaction. N-Methoxysulfonamide was further exploited for the synthesis of symmetrical biaryls in the presence of CuCl₂.

Ni(ii)-Catalyzed intermolecular selective Heck-type arylation of unactivated alkenes with arylboronic acids

This work: directing group-assisted Ni(ii)-catalyzed intermolecular Heck arylation of unactivated alkenes.

Amine-Directed Mizoroki-Heck Arylation of Free Allylamines

The transition metal-catalyzed Mizoroki−Heck reaction is a powerful method to synthesize C–C bonds, allowing access to several important pharmaceuticals. Traditionally free amines have not been compatible with these approaches due...

Synthesis of chiral branched allylamines through dual photoredox/nickel catalysis

Allylamines are versatile building blocks in the synthesis of various naturally occurring products and pharmaceuticals. In contrast to terminal allylamines, the methods of synthesis of their branched congeners with internal, stereodefined double bonds are less explored. This work describes a new approach for the preparation of allylamines via cross-coupling of alkyl bromides with simple 3-bromoallylamines by merging the photoredox approach and Ni catalysis. The reaction proceeds under mild conditions, under blue light irradiation, and in the presence of an organic dye, 4CzIPN, as a photocatalyst. The scope of suitable reaction partners is broad, including alkyl bromides bearing reactive functionalities (e.g., esters, nitriles, aldehydes, ketones, epoxides) and N-protected allylamines, as well as N-allylated secondary and tertiary amines and heterocycles. The employment of non-racemic starting materials allows for rapid and easy construction of complex multifunctional allylamine derivatives without the loss of enantiomeric purity.

Palladium-Catalyzed γ,γ'-Diarylation of Free Alkenyl Amines

The direct difunctionalization of alkenes is an effective way to construct multiple C-C bonds in one-pot using a single functional group. The regioselective dicarbofunctionalization of alkenes is therefore an important area of research to rapidly obtain complex organic molecules. Herein, we report a palladium-catalyzed γ,γ'-diarylation of free alkenyl amines through interrupted chain walking for the synthesis of Z-selective alkenyl amines. Notably, while 1,3-dicarbofunctionalization of allyl groups is well precedented, the present disclosure allows 1,3-dicarbofunctionalization of highly substituted allylamines to give highly Z-selective trisubsubstituted olefin products. This cascade reaction operates via an unprotected amine-directed Mizoroki-Heck (MH) pathway featuring a β-hydride elimination to selectively chain walk to furnish a new terminal olefin which then generates the cis-selective alkenyl amines around the sterically crowded allyl moiety. This operationally simple protocol is applicable to a variety of cyclic, branched, and linear secondary and tertiary alkenylamines, and has a broad substrate scope with regard to the arene coupling partner as well. Mechanistic studies have been performed to help elucidate the mechanism, including the presence of a likely unproductive side C-H activation pathway.

Recent advances in aminative difunctionalization of alkenes

Alkenes are versatile building blocks in modern organic synthesis. In the difunctionalization reactions of alkenes, two functional groups can be simultaneously introduced into the π system. This is an efficient strategy for the synthesis of multifunctional compounds with complex structures and has the advantages of atom and step economy. Nitrogen-containing organic compounds are widely found in natural products and synthetic compounds, such as dyes, pesticides, medicines, artificial resins, and so on. Many natural products with high biological activity and a broad range of drugs have nitrogen-containing functional groups. The research on the construction methods of C-N bonds has always been one of the most important tasks in organic synthesis, especially in drug synthesis, and the synthetic methods starting from simple and easily available raw materials have been a topic of interest to chemists. The aminative difunctionalization of alkenes can efficiently construct C-N bonds, and at the same time, prepare some compounds that usually require multiple steps of reaction. It is one of the most effective strategies for the simple and efficient synthesis of functionalized nitrogen-containing compounds. This review outlines the major developments focusing on the transition metal-catalyzed or metal-free diamination, aminohalogenation, aminocarbonation, amino-oxidation and aminoboronation reactions of alkenes from 2015-2020.

Palladium-Catalyzed Regioselective Arylation of Unprotected Allylamines

Palladium-catalyzed organometallic transformations of free amines are often unsuccessful due to side reactions, such as oxidation, that can occur. However, the ability to furnish the free amine products from these reactions is important for improving the utility and sustainability of these processes, especially for accessing their potential as medicinal and agrochemical agents. Notably, the 3,3-diarylallylamine motif is prevalent in a variety of biologically relevant structures, yet there are few catalytic approaches to their synthesis, and none involving the free amine. Herein, we describe a simple protocol for the arylation of cinnamylamines and the diarylation of terminal allylamines to generate a diverse group of 3,3-diarylallylamine products using a PdII precatalyst. Key features of the method are the ability to access relatively mild conditions that facilitate a broad substrate scope as well as direct diarylation of terminal allylamine substrates. In addition, several complex and therapeutically relevant molecules are included to demonstrate the utility of the transformation.

Pd-Catalyzed Oxidative Heck Reaction of Grignard Reagents with Diaziridinone as Oxidant

A novel Pd-catalyzed oxidative Heck reaction with readily available Grignard reagents using di- t-butyldiaziridinone as an oxidant has been developed. Various substituted olefins were obtained in 46-91% yields with high regioselectivity under mild reaction conditions.

Fluoroalkenylation of boronic acids via an oxidative Heck reaction

A fluoroalkenylation of boronic acids with fluoroalkyl alkenes has been developed. The Pd-catalyzed oxidative Heck coupling reaction proceeds under an oxygen atmosphere at room temperature, in the absence of a base and/or a ligand, showing excellent practicality of the process. This simple transformation is highly stereoselective to provide only E-isomers. In addition to the general approach using alkenes with functionalized fluoroalkyl reagents, this method, by transferring an aromatic system to the electron-deficient fluoroalkyl alkene, provides an efficient alternative method to yield valuable organofluorines.

Rhodium(i)-catalysed decarbonylative direct C–H vinylation and dienylation of arenes

Rh(i)-Catalyzed decarbonylative direct C–H bond vinylation and dienylation of arenes with acrylic acid and (E)-penta-2,4-dienoic acid have been developed.

Vinyluridine as a Versatile Chemoselective Handle for the Post-transcriptional Chemical Functionalization of RNA

The development of modular and efficient methods to functionalize RNA with biophysical probes is very important in advancing the understanding of the structural and functional relevance of RNA in various cellular events. Herein, we demonstrate a two-step bioorthogonal chemical functionalization approach for the conjugation of multiple probes onto RNA transcripts using a 5-vinyl-modified uridine nucleotide analog (VUTP). VUTP, containing a structurally noninvasive and versatile chemoselective handle, was efficiently incorporated into RNA transcripts by in vitro transcription reactions. Furthermore, we show for the first time the use of a palladium-mediated oxidative Heck reaction in functionalizing RNA with fluorogenic probes by reacting vinyl-labeled RNA transcripts with appropriate boronic acid substrates. The vinyl label also permitted the post-transcriptional functionalization of RNA by a reagent-free inverse electron demand Diels-Alder (IEDDA) reaction in the presence of tetrazine substrates. Collectively, our results demonstrate that the incorporation of VUTP provides newer possibilities for the modular functionalization of RNA with variety of reporters.

Intramolecular oxyacetoxylation of N-allylamides: an expeditious synthesis of oxazolines and oxazines by using a PhI(OAc)2/hydrogen fluoride-pyridine system

The synthesis of oxazolines and oxazines from N-allylamides was accomplished via an unprecedented reaction set. This reaction involved an intramolecular cyclization of N-allylamides resulting from nucleophilic attack of the allylamine on the benzoxazin-4-one. Unlike the previous literature, the isolable N-allylamide could readily be subjected to exo and endo fashion ring-closure under conditions to afford the title compounds.

Open-air oxidative Mizoroki–Heck reaction of arylsulfonyl hydrazides with alkenes

A palladium(ii)-catalyzed oxidative Mizoroki–Heck reaction of arylsulfonyl hydrazides with alkenes was developed employing Pd(OAc)₂ and pyridine ligand L9 as a catalyst system and ​atmospheric air as the sole oxidant in an open-vessel manner.