A General Strategy for Sustainable 3D Printing Based on A Multifunctional Photoinitiator.

A multifunctional photoinitiator is presented, offering precise control over light-induced polymerization initiation at 450 nm and material degradation at 365 nm. This is accomplished by covalently linking photoactive bis(acyl)phosphane oxide and photocleavable o-nitrobenzyl ether moieties onto the surface of γ-cyclodextrin. Upon degradation, the resulting linear polymers can be easily re-dissolved in their corresponding monomer and re-cured, exhibiting superior mechanical properties compared to the pristine material. Moreover, this photoinitiator enables the successful 3D printing of intricate and precise structures, representing a promising general strategy for developing recyclable photoresins for 3D printing applications.

Additive Manufacturing of Micro-Architected Copper based on an Ion-Exchangeable Hydrogel.

Additive manufacturing (AM) of copper through laser-based processes poses challenges, primarily attributed to the high thermal conductivity and low laser absorptivity of copper powder or wire as the feedstock. Although the use of copper salts in vat photopolymerization-based AM techniques has garnered recent attention, achieving micro-architected copper with high conductivity and density has remained elusive. In this study, we present a facile and efficient process to create complex 3D micro-architected copper structures with superior electrical conductivity and hardness. The process entails the formulation of an ion-exchangeable photoresin, followed by the utilization of digital light processing (DLP) printing to sculpt 3D hydrogel scaffolds, which were transformed into Cu2+-chelated polymer frameworks (Cu-CPFs) with a high loading of Cu2+ ions through ion exchange, followed by debinding and sintering, results in the transformation of Cu-CPFs into miniaturized copper architectures. This methodology represents an efficient pathway for the creation of intricate micro-architected 3D metal structures.

Synthesis of Unsymmetrical Trisulfides from S-Substituted Sulphenylthiosulphates.

Trisulfide unit is widely found in natural products and has garnered attention due to the unique pharmacological and physiochemical properties. However, despite limited progress, widely applicable approaches for constructing unsymmetrical trisulfides have so far remain scarce. In this work, an easy-to-prepare, solid-state and scalable reagent, S-substituted sulphenylthiosulphate, has been developed for the divergent synthesis of unsymmetrical trisulfides. Alkyl electrophile substrates, including bromides, chlorides, iodides and tosylates, with diverse substituents are smoothly converted to the corresponding trisulfides with S-substituted sulphenylthiosulphates and thiourea as another sulfur source. Furthermore, the late-stage modification of drug molecules was successfully achieved through this method.

Synthesis of N-Difluoromethyl Carbonyl Compounds from N-Difluoromethylcarbamoyl Fluorides.

Fluorinated small molecules are commonly used in functional small-molecule chemistry, and N-difluoromethyl (N-CF2H) compounds are particularly intriguing due to their unique and unexplored physiochemical properties. However, despite limited progress, a general methodological approach to the synthesis of N-CF2H compounds remains elusive. Here, guided by computation, we present a simple and practical protocol to access N-CF2H amides and related carbonyl derivatives. The protocol involves a one-pot conversion of thioformamides through desulfurization-fluorination and acylation, providing N-difluoromethylcarbamoyl fluoride building blocks that can be further diversified to a variety of unexplored N-CF2H carbonyl compounds with rich functionality. Additionally, preliminary studies on their properties and stability showcased their potential application in pharmaceuticals and agrochemicals.

Fluorine-Containing Functional Group-Based Energetic Materials.

Molecules featuring fluorine-containing functional groups exhibit outstanding properties with high density, low sensitivity, excellent thermal stability, and good energetic performance due to the strong electron-withdrawing ability and high density of fluorine. Hence, they play a pivotal role in the field of energetic materials. In light of current theoretical and experimental reports, this review systematically focuses on three types of energetic materials possessing fluorine-containing functional groups F- and NF2 - substituted trinitromethyl groups (C(NO2 )2 F, C(NO2 )2 NF2 ), trifluoromethyl group (CF3 ), and difluoroamino and pentafluorosulfone groups (NF2 , SF5 ) and investigates the synthetic methods, physicochemical parameters, and energetic properties of each. The incorporation of fluorine-containing functional moieties is critical for the development of novel high energy density materials, and is rapidly being adopted in the design of energetic materials.

Asymmetric Allylic Substitution-Isomerization for the Modular Synthesis of Axially Chiral N-Vinylquinazolinones.

Axially chiral N-substituted quinazolinones are important bioactive molecules, which are presented in many synthetic drugs. However, most strategies toward their atroposelective synthesis are mainly limited to the axially chiral arylquinazolinone frameworks. The development of modular synthetic methods to access diverse quinazolinone-based atropisomers remains scarce and challenging. Herein, we report the regio- and atroposelective synthesis of axially chiral N-vinylquinazolinones via the strategy of asymmetric allylic substitution-isomerization. The catalysis system utilized both asymmetric transition-metal catalysis and organocatalysis to efficiently afford trisubstituted and tetrasubstituted N-vinylquinazolinone atropisomers, respectively. With the meticulous design of ß-substituted allylic substrates, both Z- and E-tetrasubstituted axially chiral N-vinylquinazolinones were obtained in good yields and high enantioselectivities.

Functional Polythioamides Derived from Thiocarbonyl Fluoride.

Polythioamide is a unique type of sulfur-containing polymer with advanced functionalities. Nonetheless, the elemental sulfur commonly used in their synthesis tends to react readily with unsaturated functional groups, thereby limiting the scope of eligible substrates. Inspired by the highly efficient sulfur-fluoride exchange (SuFEx) polymerization through discrete hubs, we present herein a pioneering and versatile approach to the synthesis of polythioamides from diboronic acids, secondary diamines, and thiocarbonyl fluoride as the central connective hub. Well-defined structures, including previously inaccessible unsaturated substrates, were realized. These newly devised polythioamides can efficiently and selectively bind to metal ions and were applied in precious-metal recovery. Further development resulted in PdII -crosslinked single-chain nanoparticles serving as recyclable homogeneous catalysts, thus demonstrating the vast potential of these unprecedented polythioamides. We anticipate that thiocarbonyl fluoride could emerge as a potent hub for facilitating the intricate synthesis of sulfur-containing polymers.

Stepwise Asymmetric Allylic Substitution-Isomerization Enabled Mimetic Synthesis of Axially Chiral B,N-Heterocycles.

Axially chiral molecules bearing multiple stereogenic axes are of great importance in the field of organic chemistry. However, the efficient construction of atropisomers featuring two different types of stereogenic axes has rarely been explored. Herein, we report the novel atroposelective synthesis of configurationally stable axially chiral B,N-heterocycles. By using stepwise asymmetric allylic substitution-isomerization (AASI) strategy, diaxially chiral B,N-heterocycles bearing B-C and C-N axes that are related to the moieties of axially chiral enamines and arylborons were also obtained. In this case, all four stereoisomers of diaxially chiral B,N-heterocycles were stereodivergently afforded in high enantioselectivities. Density functional theory (DFT) studies demonstrated that the NH⋅⋅⋅π interactions played a unique role in the promotion of stereospecific isomerization, thereby leading to the highly efficient central-to-axial chirality transfer.

General Access to N-CF3 Secondary Amines and Their Transformation to N-CF3 Sulfonamides.

The synthesis of N-CF3 compounds through fluorination or trifluoromethylation of N-containing compounds has been extensively investigated. However, general access to N-CF3 compounds simply from N-CF3 secondary amines is hampered by the challenging preparation and instability of these amines, as well as a much lower reactivity due to the strong electron-withdrawing nature and steric bulk of the trifluoromethyl moiety. Herein, we report a general and highly efficient synthesis of N-CF3 secondary amines with excellent isolated yields via the addition of the in situ generated difluoromethyl imine (R-N=CF2 ) intermediates with hydrogen fluoride, which is mildly produced by triethylsilane and silver fluoride. N-CF3 sulfonamides, highly desirable but scarce at present, are easily accessible from these valuable building blocks through an unprecedented route. This study will bring new vitality to the synthesis of N-CF3 compounds.

Tandem Iridium Catalysis as a General Strategy for Atroposelective Construction of Axially Chiral Styrenes.

Axially chiral styrenes are of great interest since they may serve as a class of novel chiral ligands in asymmetric synthesis. However, only recently have strategies been developed for their enantioselective preparation. Thus, the development of novel and efficient methodologies is highly desirable. Herein, we reported the first tandem iridium catalysis as a general strategy for the synthesis of axially chiral styrenes enabled by Asymmetric Allylic Substitution-Isomerization (AASI) using cinnamyl carbonate analogues as electrophiles and naphthols as nucleophiles. In this approach, axially chiral styrenes were generated through two independent iridium-catalytic cycles: iridium-catalyzed asymmetric allylic substitution and in situ isomerization via stereospecific 1,3-hydride transfer catalyzed by the same iridium catalyst. Both experimental and computational studies demonstrated that the isomerization proceeded by iridium-catalyzed benzylic C-H bond oxidative addition, followed by terminal C-H reductive elimination. Amid the central-to-axial chirality transfer, the hydroxyl of naphthol plays a crucial role in ensuring the stereospecificity by coordinating with the Ir(I) center. The process accommodated broad functional group compatibility. The products were generated in excellent yields with excellent to high enantioselectivities, which could be transformed to various axially chiral molecules.

Synthesis of Thiocarbamoyl Fluorides and Isothiocyanates Using Amines with CF3SO2Cl.

A practical and efficient method to synthesize thiocarbamyl fluorides and isothiocyanates from amines with trifluoromethanesulfonyl chloride was developed. In the presence of the reducing agent triphenylphosphine and sodium iodide, thiocarbamyl fluorides and isothiocyanates were synthesized from secondary/primary amine in moderate to excellent yields, respectively. A broad scope of substrates and good functional group compatibility were observed.

Regioselective Chlorothiolation of Alkenes with Sulfonyl Chlorides.

Newly developed sulfonyl chloride-based regioselective chlorothiolation of alkenes has been disclosed; the reaction is compatible with a variety of functional groups and can be scaled up to the gram scale with no loss in yield. The employment of readily available reactants, mild reaction conditions, and high regioselectivity makes this process very practical. Mechanistic studies revealed a possible free radical reaction pathway.

Fluoromethoxymethylation of Nitrogen Heterocyclic Compounds with Fluoromethyl Iodide.

The fluoromethoxymethylation of nitrogen heterocyclic compounds with fluoromethyl iodide has been reported for the first time. In this reaction, a number of unexplored fluoromethoxymethylated nitrogen heterocyclic compounds including indoles, carbazoles, and 1H-indazoles were efficiently formed. Mechanistic studies indicated that this transformation consists of electrophilic monofluoromethylation, rapid hydrolysis, and another electrophilic monofluoromethylation. This method makes it possible to synthesize complex bioactive molecules containing a CH2OCH2F group, which have the potential to be a new series of fluorine-containing chemical entities for medicinal chemists.

Trifluoromethanesulfinyl Chloride for Electrophilic Trifluoromethythiolation and Bifunctional Chlorotrifluoromethythiolation.

Trifluoromethanesulfinyl chloride (CF3 SOCl) has been introduced as a new reagent for C-H trifluoromethylthiolation of indoles, thiophenes, and ketones under catalyst-free conditions and in the absence of reductant. The disproportionation of CF3 SOCl to CF3 SO2 Cl and CF3 SCl provides two pathways for the trifluoromethylthiolation. Direct trifluoromethylthiolation with CF3 SCl or trifluoromethylsulfoxidation with CF3 SOCl is followed by reduction with CF3 SOCl. This reagent can be used to functionalize benzothiophenes, benzofurans, and indenes under the promotion of Ag2 CO3 . It can also be used for trifluoromethylthiolation of thiols and benzeneselenols, and 1,2-bifunctional chlorotrifluoromethylthiolation of indoles, styrenes, and alkyenes. The method can also be extended for difluorometylthiolation reactions using CF2 HSOCl.

Metal-Free Electrophilic Trifluoroethylthiolation with NaSO2CH2CF3.

Metal-free trifluoroethylthiolation with fluorinated sulfinate salt NaSO2CH2CF3 under reductive conditions has been developed. The strategy enables the installation of the SCH2CF3 moiety efficiently to form a number of unexplored stable trifluoroethylthiolated heterocycles, arenes, and thiols, which have the potential to be a new series of fluorine-containing chemical entities for medicinal chemists.

Acid/Phosphide-Induced Radical Route to Alkyl and Alkenyl Sulfides and Phosphonothioates from Sodium Arylsulfinates in Water.

A newly developed aqueous system with acid and phosphide was introduced in which odorless and stable sodium arylsulfinates can in situ generate arylsulfenyl radicals. These radicals have high reactivity to react with alkynes, alkenes, and H-phosphine oxides for the synthesis of alkyl and alkenyl sulfides and phosphonothioates. The control experiments and quantum calculations are also performed to gain insights into the generation mechanism of arylsulfenyl radicals. Notably, the chemistry is free of thiol odors, organic solvents, and metals.

Copper-catalyzed fluoroalkylation of alkynes, and alkynyl & vinyl carboxylic acids with fluoroalkyl halides.

Copper-catalyzed fluoroalkylation of alkynes and alkynyl carboxylic acids has been achieved with high functional-group tolerance and excellent regio- and stereoselectivities. A variety of fluoroalkyl halides including ethyl bromodifluoroacetate can be employed. Additionally, an unprecedented decarboxylative fluoroalkylation of α, ß-unsaturated carboxylic acids has been achieved via a radical pathway.

Organocatalytic One-Pot Asymmetric Synthesis of Thiolated Spiro-γ-lactam Oxindoles Bearing Three Stereocenters.

The first asymmetric synthesis of spiro-γ-lactam oxindoles bearing three stereocenters is reported. One-pot thiol-Michael/Mannich/lactamization reactions promoted by a recyclable fluorous bifunctional cinchona alkaloid/thiourea organocatalyst afford products in moderate to good yields with up to 95% ee and 6:1 dr.

Transition-metal-free C-H oxidative activation: persulfate-promoted selective benzylic mono- and difluorination.

An operationally simple and selective method for the direct conversion of benzylic C-H to C-F to obtain mono- and difluoromethylated arenes using Selectfluor™ as a fluorine source is developed. Persulfate can be used to selectively activate benzylic hydrogen atoms toward C-F bond formation without the aid of transition metal catalysts.

Direct Trifluoromethylthiolation and Perfluoroalkylthiolation of C(sp(2))-H Bonds with CF3SO2Na and RfSO2Na.

A new method for CF3SO2Na-based direct trifluoromethylthiolation of C(sp(2))-H bonds has been developed. CF3SSCF3 is generated in situ from cheap and easy-to-handle CF3SO2Na, and in the presence of CuCl can be used for electrophilic trifluoromethylthiolation of indoles, pyrroles, and enamines. The method has been extended to perfluoroalkylthiolation reactions using RfSO2Na.