Robby Vroemans

This review details current advancements in synthesizing cryptophane host molecules post the 2009 comprehensive review by Brotin and Dutasta. It categorizes literature based on methods for creating the cryptophane core and evolving late-stage functionalization techniques. Focus is placed on template synthesis, coupling, late-stage functionalization, small-molecule binding, and some applications.

Abstract

This review covers the latest developments in the synthesis of cryptophane host molecules since the publication of the last extensive review by Brotin and Dutasta in 2009. The literature has been categorized according to the synthetic method for generating the cryptophane core and we also emphasize emerging late-stage functionalization approaches. The synthetic strategies towards cryptophanes can be broadly categorized into the well-established direct- (two-step), template- and coupling (or capping) methods. The examples covered in this review mainly highlight template-based synthesis, coupling approaches and late-stage functionalization.

Publication date: 15 January 2024

Source: Molecular Catalysis, Volume 553

Author(s): Jianhua Fan, Xin Wang, Jing Ma, Xingman Liu, Jianbo Wu, Yingtao Liu

Publication date: 1 March 2024

Source: Coordination Chemistry Reviews, Volume 502

Author(s): Chunmei Li, Jilong Wang, Lei Tong, Yun Wang, Pingfan Zhang, Mingshan Zhu, Hongjun Dong

Publication date: 30 January 2024

Source: Tetrahedron, Volume 151

Author(s): Ilnett García-Ventura, Diego A. Roa, Juventino J. García

α-Hydroxycarboxamide moiety of oxazaborolidinone (OxB) dynamically covers the Lewis acidic boron center, providing stabilizing effects on unstable boronic acids including 2-furyl, vinyl, and alkyl groups and protective effects on OxB with haloaryl groups. Reported protection is useful for iterative couplings and Suzuki–Miyaura coupling reactions with OxBs prepared from unstable arylboronic acids.

Abstract

It was demonstrated that α-hydroxycarboxamide is an excellent boron-protecting group. The reaction between α-hydroxycarboxamide and organoboronic acids produced stable oxazaborolidinones (OxBs), in which the -hybridized boron atom was sterically protected by α-hydroxycarboxamide. The alkyl groups of the α-hydroxycarboxamide moiety can dynamically cover the p-orbital of the -hybridized boron center, creating a small space around the boron atom, allowing for smooth transmetalation by a Pd catalyst and easy deprotection by water. This protecting phenomenon is effective for readily purification, Suzuki–Miyaura coupling reactions with unstable boronic acids and iterative cross-couplings.

Comprehensive Summary

The deuteration of organic compounds has attracted more attentions in recent years for the potential applications in new drug discovery and synthetic chemistry. For this purpose, many efficient deuterium labeling methodologies have been developed, including hydrogen isotope exchange (HIE), reductive deuteration, and dehalogenative deuteration that allow for the synthesis of selectively deuterated compounds. In the last few years, great breakthroughs in selective isotope labeling have been achieved and the interest in new methodologies for the deuteration of organic molecules is rising. In this review, we summarized the recent developments in the selective deuteration of organic molecules since 2021. Several types of key processes in deuterium incorporation reactions, including H/D exchange, reductive deuteration and dehalogenative deuteration, are introduced and discussed.

Key Scientists

In the 2000s, Derdau and Atzrodt's group have made great contributions to the directing group assisted noble-metal catalyzed hydrogen isotope exchange of arenes and applications of labeled compounds. During the same period, Sajiki and co-workers completed a series of deuteration reactions by heterogeneous platinum-group metal catalysts. Since 2015, Gregory Pieters and co-workers have developed ruthenium catalysts for selective hydrogen isotope exchange. In 2016, Chirik's group achieved hydrogen isotope exchange in the presence of a homogeneous iron complex. David MacMillan and coworkers have made breakthroughs in photocatalyzed HIE reactions for α-amino C(sp³)–H bonds. From 2020, a series of nanoelectrodes were designed for selective dehalogenative deuterations and reductive deuteration of unactivated unsaturated bonds by Zhang's group. Recently, Beller's group developed several efficient strategies for isotopic labeling using heterogeneous earth-abundant catalysts. Our review summarized the latest and important developments since 2021.

Publication date: 15 January 2024

Source: Molecular Catalysis, Volume 553

Author(s): Cristina Bilanin, Yongkun Zheng, Alejandro Vidal–Moya, Emilio Pardo, Marta Mon, Antonio Leyva–Pérez

Publication date: 30 January 2024

Source: Tetrahedron, Volume 151

Author(s): Tao Wang, Mengyue Wu, Shuangjie Qiu, Hongjun Ming, Yunge Yuan, Mengjiao Liu, Jiankang Yue, Fangzhi Huang

Abstract

In this paper, we present a one-pot protocol that enables a straightforward and selective transformation of alkyl benzothiazol-2-yl and phenyltetrazol-2-yl sulfones and acyl chlorides into ketones, E-olefins, Z-olefins, and even pyrroles. The final product of the reaction depends on the proper choice of the reaction workup. Notably, the protocol designed for olefin formation allows a switch between E- and Z-olefin formation by the correct choice of the reaction workup. These developed protocols facilitate the formation of all compounds under mild reaction conditions, as evidenced by the synthesis of (nitro)-fatty acids, and the concept can be extended to other product formations, as demonstrated by the synthesis of pyrroles.

The Front Cover represents the substantial number of possible pathways for guaiacol hydrodeoxygenation (HDO) as a hedge maze. Flags dotted throughout the maze illustrate the intermediates and products associated with each route. The arrows on the signpost, each marked with a different transition metal, point the guaiacol molecule in different directions, symbolising the importance of catalyst choice on the mechanistic chemistry of HDO. In their Research Article, A. Roldan and co-workers present an exhaustive microkinetic analysis of the mechanistic chemistry behind guaiacol HDO, utilising the results of over 300 DFT models of the intermediates. Highly desirable kinetics for deoxygenation and hydrogenation were reported over Ni(111) at industrial temperatures, which was shown to progress through a catechol intermediate. More information can be found in the Research Article by A. Roldan and co-workers.

Publication date: 15 January 2024

Source: Molecular Catalysis, Volume 553

Author(s): Veronika D Badazhkova, Risto Savela, Johan Wärnå, Dmitry Yu Murzin, Reko Leino

The Front Cover shows illustrates the practical continuous-flow system for hydrogen production from formic acid using an iridium-immobilized catalyst based on polyethyleneimine (PEI) showcased as a yellow solid powder. It also depicts power generation through a fuel cell. The catalytic activity, expressed as turnover frequency (TOF value), is 73 200 h^-1, with durability exceeding 2000 h without any degradation. The system has achieved continuous electric power generation for over 5 h on a laboratory scale. More information can be found in the Research Article by K. Sawahara et al.

Sulfur-containing 1,2,3-triazoles display bioactivities. Numerous approaches have been established to form sulfur-containing 1,2,3-triazoles. In this review, the synthesis and properties of sulfur-containing 1,2,3-triazoles, including 4-sulfanyl-1,2,3-triazoles, 5-sulfanyl-1,2,3-triazoles, N-sulfonyl-1,2,3-triazoles, 4-sulfonyl-1,2,3-triazoles, 5-sulfonyl-1,2,3-triazoles, sulfur- and heteroatom-containing 1,2,3-triazoles, were highlighted.

Abstract

Sulfur-containing 1,2,3-triazoles display bioactivities like antidepressant, antifungal activity, antitumor, etc. Numerous approaches have been established to form sulfur-containing 1,2,3-triazoles. 4-Sulfanyl- and 5-sulfanyl-1,2,3-triazoles were produced by metal-catalyzed azide-alkyne cycloaddition (AAC), etc. N-Sulfonyl-1,2,3-triazoles were generated via the reaction of acetylides with sulfonyl azides, CuAAC. 4-Sulfonyl-1,2,3-triazoles were produced through [3+2] cycloaddition and reaction of azide with bromovinylsulfonyl fluoride. Although 5-sulfonyl-1,2,3-triazoles were formed successfully via RuAAC, their synthetic approaches were very limited. 1-Phosphinyl-2-sulfanylethynes were suitable substances to access sulfur- and phosphorus-containing triazoles. In this review, the synthesis and properties of sulfur-containing 1,2,3-triazoles were highlighted. Initially, the properties of organosulfurs, 1,2,3-triazoles and sulfur-containing 1,2,3-triazoles were briefly introduced. After stating the general procedures to construct 1,2,3-triazole skeleton, the synthetic approaches and properties of sulfur-involved 1,2,3-triazoles were sorted and described in details. According to different kinds of sulfur-containing 1,2,3-triazoles, synthetic methods and features of 4-sulfanyl-1,2,3-triazoles, 5-sulfanyl-1,2,3-triazoles, N-sulfonyl-1,2,3-triazoles, 4-sulfonyl-1,2,3-triazoles, 5-sulfonyl-1,2,3-triazoles, sulfur- and heteroatom-containing 1,2,3-triazoles were summarized.

The uncatalyzed N-alkylation of primary amines is made possible by a dual tunable plasma-microdroplet reaction platform utilizing the in-situ generation of reactive oxygen species during electrospray. Dual tunability is achieved by controlling the reagent concentration and timescale of reaction, allowing selective formation of single and double N-alkylated products. Products are validated online via mass spectrometry and readily collected yielding milligram quantities in a preparative approach, as reported by Abraham K. Badu-Tawiah et al. in their Research Article (e202311100).

A nanographene with a tri-N-doped cavity was synthesized by photo-induced cyclization. In comparison with nitrogen-doping at the edge, this tri-N-doped holey nanographene exhibited markedly reduced basicity and selective affinity toward Ag⁺. This nanographene with a N-doped cavity provides a precise model for understanding the binding in the nano-confined defects of graphenic materials.

Abstract

Nitrogen-doped cavities are pervasive in graphenic materials, and represent key sites for catalytic and electrochemical activity. However, their structures are generally heterogeneous. In this study, we present the synthesis of a well-defined molecular cutout of graphene featuring N-doped cavity. The graphitization of a macrocyclic pyridinic precursor was achieved through photochemical cyclodehydrochlorination. In comparison to its counterpart with pyridinic nitrogen at the edges, the pyridinic nitrogen atoms in this nanographene cavity exhibit significantly reduced basicity and selective binding to Ag⁺ ion. Analysis of the protonation and coordination equilibria revealed that the tri-N-doped cavity binds three protons, but only one Ag⁺ ion. These distinct protonation and coordination behaviors clearly illustrate the space confinement effect imparted by the cavities.

Abstract

An EDA complex comprising N-allyl bromodifluoroacetamides and tertiary alkyl amine was exploited to facilitate annulative difunctionalization reaction under visible-light irradiation. This external photocatalyst-free methodology garners olefin-olefin coupling featuring a radical Truce-Smiles rearrangement and produced long-chain functionalized gem-difluoropyrrolidones from N-substituted methacryloyl sulfonamides, while simple N-aryl methacrylamides furnished pyrrolidinone-oxindole hybrid lactams in high yields. Mechanistic investigations substantiate a combined reaction mechanism, involving charge-transfer EDA complex-based radical cascade, alongside an α-aminoalkyl radical-triggered XAT process, exhibiting a quantum yield value of 1.48.

Abstract

An arylation of anions of active methylene compounds with aryl halides provides an access to synthetically versatile α-arylated 1,3-diketones, β-keto esters, β-keto nitriles, β-cyano esters, etc. Previously, these C−C cross-coupling reactions have been accomplished only using transition metal-based catalysts. Herein, we demonstrate that these arylations can be successfully realized under catalyst-free conditions employing the electron donor-acceptor (EDA) complex photoactivation strategy. The protocol was further optimized for a semi-one pot synthesis of indole derivatives via an intramolecular C−C coupling.

A mechanochemical nitrene transfer reaction towards N-acyl sulfonimidamides from sulfinamides and dioxazolones with the catalysis of iron(II) chloride is presented. This one-step solvent-free procedure shows better conversions rate and chemoselectivity compared to its solution-phase counterpart, providing a wide range of N-acyl sulfonimidamides in up to 87 % yield. Mechanistically, crucial nitrene iron complex intermediates are suggested by ESI-MS.

Abstract

A mechanochemical synthesis of sulfonimidamides by iron(II)-catalyzed exogenous ligand-free N-acyl nitrene transfer to sulfinamides is reported. The one-step method tolerates a wide range of sulfinamides with various substituents under solvent-free ambient conditions. Compared to its solution-phase counterpart, this mechanochemical approach shows better conversion and chemoselectivity. Mechanistic investigations by ESI-MS revealed the generation of crucial nitrene iron intermediates.

The synthesis and properties of nonaromatic stable NIR-absorbing phenothiazine-embedded heteroporphyrins and their monoprotonated and diprotonated derivatives are described.

Abstract

A series of phenothiazine embedded heteroporphyrins containing one phenothiazine unit, two pyrrole rings and one heterocycle such as furan, thiophene, selenophene and tellurophene connected via four meso carbons were synthesized. The macrocycles were synthesized by condensing the phenothiazine based tripyrrane with corresponding 2,5-bis(hydroxymethyl)heterocycle under BF₃ ⋅ OEt₂ catalyzed conditions and compared the structural, spectral, and electrochemical properties with the reported phenothiazinophyrins. The studies showed that the phenothiazine embedded heteroporphyrins were nonaromatic and electronic properties were significantly altered by replacing the pyrrole ring from phenothiazinophyrin with different heterocycles. The X-ray structure of phenothiazine embedded thiaporphyrin revealed that the macrocycle was distorted with an inverted thiophene ring. Both mono-protonated and diprotonated derivatives of macrocycles were generated by the controlled addition of trifluoroacetic acid to the macrocycles. The macrocyclic protons experienced upfield/downfield shifts in protonated derivatives compared to their corresponding neutral phenothiazine embedded heteroporphyrins. However, the heterocyclic ring in both mono- and diprotonated derivatives retained its inverted conformation. The macrocycles in their neutral and protonated form exhibit nonaromatic absorption features. The studies indicated the electron rich nature of macrocycles and DFT/TD-DFT studies were carried out to justify the experimental observations.