Intermolecular Regioselective 1,2-Diamination of Allylic Ethers

Transition-Metal-Catalyzed 1,2-Diaminations of Olefins: Synthetic Methodologies and Mechanistic Studies

1,2-Diamines are synthetically important motifs in organo-catalysis, natural products, and drug research. Continuous utilization of transition-metal based catalyst in direct 1,2-diamination of olefines, in contrast to metal-free transformations, with numerous impressive advances made in recent years (2015-2023). This review summarized contemporary research on the transition-metal catalyzed/mediated [e. g., Cu(II), Pd(II), Fe(II), Rh(III), Ir(III), and Co(II)] 1,2-diamination (asymmetric and non-asymmetric) especially emphasizing the recent synthetic methodologies and mechanistic understandings. Moreover, up-to-date discussion on (i) paramount role of oxidant and catalyst (ii) key achievements (iii) generality and uniqueness, (iv) synthetic limitations or future challenges, and (v) future opportunities are summarized related to this potential area.

Palladium-Catalyzed Organic Reactions Involving Hypervalent Iodine Reagents

The chemistry of polyvalent iodine compounds has piqued the interest of researchers due to their role as important and flexible reagents in synthetic organic chemistry, resulting in a broad variety of useful organic molecules. These chemicals have potential uses in various functionalization procedures due to their non-toxic and environmentally friendly properties. As they are also strong electrophiles and potent oxidizing agents, the use of hypervalent iodine reagents in palladium-catalyzed transformations has received a lot of attention in recent years. Extensive research has been conducted on the subject of C—H bond functionalization by Pd catalysis with hypervalent iodine reagents as oxidants. Furthermore, the iodine(III) reagent is now often used as an arylating agent in Pd-catalyzed C—H arylation or Heck-type cross-coupling processes. In this article, the recent advances in palladium-catalyzed oxidative cross-coupling reactions employing hypervalent iodine reagents are reviewed in detail.

Synergetic copper/TEMPO-catalysed benzylic C–H imidation with N-fluorobenzenesulfonimide at room temperature and tandem conversions with alcohols or arenes

A remote carbamate-directed benzylic C–H imidation with NFSI at room temperature through synergetic CuCl-TEMPO catalysis and tandem alkoxylation or arylation with alcohols or arenes are described.

Hypervalent Iodine Reagents in Palladium-Catalyzed Oxidative Cross-Coupling Reactions

Hypervalent iodine compounds are valuable and versatile reagents in synthetic organic chemistry, generating a diverse array of useful organic molecules. Owing to their non-toxic and environmentally friendly features, these reagents find potential applications in various oxidative functionalization reactions. In recent years, the use of hypervalent iodine reagents in palladium-catalyzed transformations has been widely studied as they are strong electrophiles and powerful oxidizing agents. For instance, extensive work has been carried out in the field of C–H bond functionalization via Pd-catalysis using hypervalent iodine reagents as oxidants. In addition, nowadays, iodine(III) reagents have been frequently employed as arylating agents in Pd-catalyzed C–H arylation or Heck-type cross-coupling reactions. In this review, recent advancements in the area of palladium-catalyzed oxidative cross-coupling reactions using hypervalent iodine reagents are summarized in detail.

Iodine-promoted Intermolecular Dehydrogenation Diamination: Synthesis of Unsymmetrical α,β-Diamido Ketones

Iodine-promoted direct diamination of α,β-unsaturated ketone to form two C-N bonds has been developed starting from chalcone and secondary amine. This reaction was performed in THF at 50 °C in the presence of I₂ and K₂ CO_3. The protocol is metal-free, operationally simple and carried out under mild conditions, providing an effective new way for directing diamination reactions.

Efficient metal-free aminoiodination of alkenes with N-fluorobenzenesulfonimide under mild conditions

A novel regioselective and stereoselective transition-metal-free aminoiodination of alkenes through an iodonium intermediate using NFSI as both the oxidant and amino precursor under mild conditions with a broad alkene scope is disclosed.

Metal-free C–H amination of arene with N-fluorobenzenesulfonimide catalysed by nitroxyl radicals at room temperature

The first C–H amination of arene with NFSI via organocatalysis is disclosed, which can be achieved at room temperature with a broad substrate scope.

Regiodivergent Iridium(III)-Catalyzed Diamination of Alkenyl Amides with Secondary Amines: Complementary Access to γ- or δ-Lactams

Alkenyl N-pivaloylhydroxamates undergo an Ir(III)-catalyzed diamination of the alkene with simple exogenous secondary amines under extraordinarily mild reaction conditions. The regioselectivity of the diamination is controlled by the solvent and the electronics of the cyclopentadienyl (Cpx) ligand on Ir. On the basis of a set of mechanistic experiments, we propose that the relative rates of Ir(V)-nitrenoid formation versus attack on the amido-Ir-coordinated alkene by the exogenous amine determine the outcome of the reaction.

NFSI-participated intermolecular aminoazidation of alkene through iron catalysis

An iron-catalysed intermolecular vicinal aminoazidation of alkene with NFSI is reported, with broader alkene scope comparing to previously reported aminoazidation.

Hypervalent Iodine Reagents in High Valent Transition Metal Chemistry

Over the last 20 years, high valent metal complexes have evolved from mere curiosities to being at the forefront of modern catalytic method development. This approach has enabled transformations complimentary to those possible via traditional manifolds, most prominently carbon-heteroatom bond formation. Key to the advancement of this chemistry has been the identification of oxidants that are capable of accessing these high oxidation state complexes. The oxidant has to be both powerful enough to achieve the desired oxidation as well as provide heteroatom ligands for transfer to the metal center; these heteroatoms are often subsequently transferred to the substrate via reductive elimination. Herein we will review the central role that hypervalent iodine reagents have played in this aspect, providing an ideal balance of versatile reactivity, heteroatom ligands, and mild reaction conditions. Furthermore, these reagents are environmentally benign, non-toxic, and relatively inexpensive compared to other inorganic oxidants. We will cover advancements in both catalysis and high valent complex isolation with a key focus on the subtle effects that oxidant choice can have on reaction outcome, as well as limitations of current reagents.

Stereoselective Synthesis of Cyclic Guanidines by Directed Diamination of Unactivated Alkenes

A method for a directed stereoselective guanidinylation of alkenes is described. The guanidine unit can be delivered as an intact fragment by a hydroxy or carboxy group, usually with a high level of stereocontrol. After the guanidine delivery, the directing group can be cleaved under exceptionally mild conditions, typically by alcoholysis in the presence of acetic acid. Broad functional group tolerance and mild reaction conditions for the cycloguanidilation suggest applications in medicinal chemistry and natural products synthesis.

The Quest for Palladium-Catalysed Alkyl-Nitrogen Bond Formation

Our interest in the development of transition-metal catalysis for the realisation of vicinal diamination reactions of alkenes started about a decade ago. A number of successful transformations in this area have been developed using palladium catalysis. As a challenging aspect of major importance, the palladium-catalysed coupling of alkyl-nitrogen bonds constitutes the second step in diaminations of alkenes. We here discuss the details that led us to consider high-oxidation-state palladium catalysis as a key feature in such C-N bond-forming reactions. This work discusses both our own contributions and the ones from colleagues and combines the discussion of catalytic reactions and stoichiometric control experiments. It demonstrates that reductive alkyl-nitrogen bond formation from palladium(IV) proceeds with a low activation barrier and through a linear transition state of nucleophilic displacement.

Regioselective Intermolecular Diamination and Aminooxygenation of Alkenes with Saccharin

Palladium catalysis enables the regioselective difunctionalization of alkenes using saccharin as the nitrogen source in the initial step of aminopalladation. Depending on the reaction conditions, diamination or aminooxygenation pathways can be accessed using hypervalent iodine reagents as the terminal oxidants. The aminooxygenation of allylic ethers originates from an unprecedented ambident behavior of saccharin. The participating palladium catalysts contain a palladium-saccharide unit. Two representative complexes of this type could be isolated and characterized.

Defined Palladium-Phthalimidato Catalysts for Improved Oxidative Amination

New palladium(II)-phthalimidato complexes have been synthesized, isolated, and structurally characterized. As demonstrated from over 30 examples, they constitute superior catalysts for oxidative amination reactions of alkenes with phthalimide as the nitrogen source. This work streamlines vicinal difunctionalization of alkenes and provides access to significantly improved and experimentally simplified synthetic protocols.

Intramolecular oxidative palladium-catalyzed diamination reactions of alkenyl sulfamates: an efficient synthesis of [1,2,5]thiadiazolo-fused piperazinones

A palladium-catalyzed diamination domino process of sulfamates arising from glycine allylamides is reported.

Reactivity of platinum alkyne complexes towards N-fluorobenzenesulfonimide: formation of platinum compounds bearing a β-fluorovinyl ligand

The platinum(0) alkyne complexes [Pt(L)(η(2)-PhC[triple bond, length as m-dash]CPh)] 1-4 were synthesized by reactions of [Pt(cod)2] with diphenylacetylene and a phosphine ligand precursor (1: L = dcpe, 2: L = xantphos, 3: L = κ(2)-(P,N)-iPr2PC3H6NMe2, 4: L = κ(2)-(P,N)-iPr2PC2H4NMe2). Treatment of 1 or 4 with NFSI gave the complexes [Pt(F){N(SO2Ph)2}(dcpe)] (5) and [Pt(PhC[double bond, length as m-dash]CFPh){N(SO2Ph)2}{κ(2)-(P,N)-iPr2PC2H4NMe2}] (8), whereas the reactivity of 2 and 3 towards NFSI led to product mixtures. The compounds [Pt(F){N(SO2Ph)2}(xantphos)] (6a) as well as [Pt(PhC[double bond, length as m-dash]CFPh){N(SO2Ph)2}{κ(2)-(P,N)-iPr2PC2H4NMe2}] (7a) and [Pt(PhC[double bond, length as m-dash]CFPh)(F){κ(2)-(P,N)-iPr2PC2H4NMe2}] (7b) were clearly identified. Ligand exchange reactions at 8 resulted in the formation of the β-fluorovinyl platinum(ii) complexes [Pt(PhC[double bond, length as m-dash]CFPh){OC(O)CF3}{κ(2)-(P,N)-iPr2PC2H4NMe2}] (9), [Pt(PhC[double bond, length as m-dash]CFPh)(FHF){κ(2)-(P,N)-iPr2PC2H4NMe2}] (10) and [Pt(PhC[double bond, length as m-dash]CFPh)(F){κ(2)-(P,N)-iPr2PC2H4NMe2}] (11). Treatment of 8 with dihydrogen yielded the fluorinated olefin (Z)-(1-fluoroethene-1,2-diyl)dibenzene and [Pt{N(SO2Ph)2}(H){κ(2)-(P,N)-iPr2PC2H4NMe2}] (12).

Cu(I)-catalyzed sequential diamination and dehydrogenation of terminal olefins: a facile approach to imidazolinones

Diamination of olefins presents a powerful strategy to access vicinal diamines. During the last decade, metal-catalyzed diamination of olefins has received considerable attention. This study describes an efficient sequential diamination and dehydrogenation process of terminal olefins with CuBr as catalyst and di-tert-butyldiaziridinone as nitrogen source, providing a facile and viable approach to a variety of imidazolin-2-ones, which are important structural motifs present in various biologically active molecules.

Synthesis of α, β and γ-carbolines via Pd-mediated Csp2-H/N–H activation

An efficient method for the synthesis of halo-carbolines has been developed via Pd-catalysed formation of C–N bonds through C_sp2-H/N–H activation of 4-methyl-N-[2-(pyridine-3-yl)phenyl] benzenesulfonamide derivatives.

Palladium-catalyzed intermolecular aminoacetoxylation of alkenes and the influence of PhI(OAc)2 on aminopalladation stereoselectivity

A modified protocol has been identified for Pd-catalyzed intermolecular aminoacetoxylation of terminal and internal alkenes that enables the alkene to be used as the limiting reagent. The results prompt a reassessment of the stereochemical course of these reactions. X-ray crystallographic characterization of two of the products, together with isotopic labeling studies, show that the amidopalladation step switches from a cis-selective process under aerobic conditions to a trans-selective process in the presence of diacetoxyiodobenzene.

Metal-free catalytic vicinal diamination of alkenes

The development of an intramolecular vicinal diamination protocol using metal-free conditions is discussed. The reaction uses a bromide source to generate a Br(I) catalyst in situ from a benign terminal oxidant such as sodium chlorite. The reaction is of great scope and surpasses the transition-metal catalyses developed so far for these types of reactions.

Development of intramolecular vicinal diamination of alkenes: from palladium to bromine catalysis

Palladium catalysis has been instrumental in the development of the intramolecular diamination of alkenes. Reagent combinations of a palladium catalyst and iodosobenzene diacetate or copper(II) salts, respectively, represent the broad applicability and mechanistic variation. Recent work has established alternative copper and bromine catalysts. The occupation with this reaction has also contributed to the development of high oxidation state metal catalysis in alkene difunctionalization and significantly broadened the spectrum of Pd-catalyzed C-N bond-forming reactions in general.

Catalytic asymmetric synthesis of cyclic sulfamides from conjugated dienes

This paper describes the catalytic asymmetric diamination of alkyl dienes using N,N'-di-tert-butylthiadiaziridine 1,1-dioxide in the presence of Pd(0) and a chiral phosphoramidite ligand to give cyclic sulfamides in high yield and high ee. The diamination is also amenable to gram scale.