Direct Trifluoromethylthiolation of Unactivated C(sp3)?H Using Silver(I) Trifluoromethanethiolate and Potassium Persulfate

A practical and efficient method for the direct trifluoromethylthiolation of unactivated C(sp³) H bonds by AgSCF₃/K₂S₂O₈ under mild conditions is described. The reaction has a good functional‐group tolerance and good selectivity. Initial mechanistic investigations indicate that the reaction may involve a radical process in which K₂S₂O₈ plays key roles in both the activation of the C(sp³) H bond and the oxidation of AgSCF₃.     

Direct Trifluoromethylthiolation of Unactivated C(sp3)H Using Silver(I) Trifluoromethanethiolate and Potassium Persulfate

A practical and efficient method for the direct trifluoromethylthiolation of unactivated C(sp³)? H bonds by AgSCF₃/K₂S₂O₈ under mild conditions is described. The reaction has a good functional‐group tolerance and good selectivity. Initial mechanistic investigations indicate that the reaction may involve a radical process in which K₂S₂O₈ plays key roles in both the activation of the C(sp³)? H bond and the oxidation of AgSCF₃.     

Visible‐Light‐Driven Palladium‐Catalyzed Radical Alkylation of C−H Bonds with Unactivated Alkyl Bromides

Reported herein is a novel visible‐light photoredox system with Pd(PPh₃)₄ as the sole catalyst for the realization of the first direct cross‐coupling of C(sp³)−H bonds in N‐aryl tetrahydroisoquinolines with unactivated alkyl bromides. Moreover, intra‐ and intermolecular alkylations of heteroarenes were also developed under mild reaction conditions. A variety of tertiary, secondary, and primary alkyl bromides undergo reaction to generate C(sp³)−C(sp³) and C(sp²)−C(sp³) bonds in moderate to excellent yields. These redox‐neutral reactions feature broad substrate scope (>60 examples), good functional‐group tolerance, and facile generation of quaternary centers. Mechanistic studies indicate that the simple palladium complex acts as the visible‐light photocatalyst and radicals are involved in the process.     

Are Organotin Reagents Derived from Bis(trimethylsilyl)picoline Suitable Precursors for the Preparation of Cyclometallated Complexes?

The organotin reagents [2‐PyC(SiMe₃)₂SnR₃] (R = Me, ⁿBu) were prepared in good yields from the reaction between the lithium salt of 2‐bis(trimethylsilyl)picoline and the corresponding trialkyltin chlorides. Reactions of these organotin reagents were carried out with various Pd and Pt complexes including [MCl₂(cod)] and [MCl₂(PhCN)₂] (M = Pd, Pt). The results show that a Me group is transferred to the metal atom, rather than the 2‐bis(trimethylsilyl)picolyl group. The mechanism for this reaction is discussed and reasons why Me group transfer occurs based on DFT computed structural data are given.     

Cobalt‐Catalyzed Cyclization of N‐Methoxy Benzamides with Alkynes using an Internal Oxidant through C−H/N−O Bond Activation

The cyclization of substituted N‐methoxy benzamides with alkynes in the presence of an easily affordable cobalt complex and NaOAc provides isoquinolone derivatives in good to excellent yields. The cyclization reaction is compatible with a range of functional group‐substituted benzamides, as well as ester‐ and alcohol‐substituted alkynes. The cobalt complex [Co^IIICp*(OR)₂] (R=Me or Ac) serves as an efficient catalyst for the cyclization reaction. Later, isoquinolone derivatives were converted into 1‐chloro and 1‐bromo substituted isoquinoline derivatives in excellent yields in the presence of POCl₃ or PBr₃.     

A Highly Efficient Gold‐Catalyzed Photoredox α‐C(sp3)H Alkynylation of Tertiary Aliphatic Amines with Sunlight

A new α‐C(sp³)? H alkynylation of unactivated tertiary aliphatic amines with 1‐iodoalkynes as radical alkynylating reagents in the presence of [Au₂(μ‐dppm)₂]²⁺ in sunlight provides propargylic amines. Based on mechanistic studies, a C? C coupling of an α‐aminoalkyl radical and an alkynyl radical is proposed for the C(sp³)? C(sp) bond formation. The mild, convenient, efficient, and highly selective C(sp³)? H alkynylation reaction shows excellent regioselectivity and good functional‐group compatibility. A scale‐up to gram quantities is possible with sunlight used as a clean and sustainable energy source.     

Synthesis,Characterization, Optical and Electrochemical Properties of Fulleropyrrolidines Containing Trifluoromethyl Group

Four novel [60]fullerene pyrrolidines containing trifluoromethyl (? CF₃) group have been synthesized via 1,3‐dipolar cycloaddition reaction, which have been characterized by UV‐Vis spectroscopy, fourier transform infrared spectroscopy, matrix‐assisted laser desorption ionization‐time of flight mass spectroscopy, and ¹H, ¹³C, ¹⁹F nuclear magnetic resonance spectrometer (¹H NMR, ¹³C NMR, ¹⁹F NMR). Their optical and electrochemical properties have been studied, and the results show that those fulleropyrrolidines containing ? CF₃ group have good fluorescence and electrochemical properties. Compared with C₆₀, they have negative shifts in varying degrees for half‐wave potentials, and may have potential applications for photovoltaic conversion materials since their lowest unoccupied molecular orbital (LUMO) levels are close to that of [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester.     

Copper‐Catalyzed Triboration of Terminal Alkynes Using B2pin2: Efficient Synthesis of 1,1,2‐Triborylalkenes

We report herein the catalytic triboration of terminal alkynes with B₂pin₂ (bis(pinacolato)diboron) using readily available Cu(OAc)₂ and PⁿBu₃. Various 1,1,2‐triborylalkenes, a class of compounds that have been demonstrated to be potential matrix metalloproteinase (MMP‐2) inhibitors, were obtained directly in moderate to good yields. The process features mild reaction conditions, a broad substrate scope, and good functional group tolerance. This copper‐catalyzed reaction can be conducted on a gram scale to produce the corresponding 1,1,2‐triborylalkenes in modest yields. The utility of these products was demonstrated by further transformations of the C?B bonds to prepare gem‐dihaloborylalkenes (F, Cl, Br), monohaloborylalkenes (Cl, Br), and trans‐diaryldiborylalkenes, which serve as important synthons and have previously been challenging to prepare.     

Silver,iron, and nickel immobilized on hydroxyapatite‐core‐shell γ‐Fe2O3 MNPs catalyzed one‐pot five‐component reactions for the synthesis of tetrahydropyridines by tandem condensation of amines,aldehydes, and methyl acetoacetate

In this study, Ag, Ni²⁺, and Fe²⁺ immobilized on hydroxyapatite‐core‐shell γ‐Fe₂O₃ nanoparticles (γ‐Fe₂O₃@HAp‐Ag, γ‐Fe₂O₃@HAp‐Ni²⁺, and γ‐Fe₂O₃@HAp‐Fe²⁺) as a new and reusable Lewis acid magnetic nanocatalyst was successfully synthesized and reported for an atom economic, extremely facile, and environmentally benign procedure for the synthesis of highly functionalized tetrahydropyridines derivatives 4a‐t is described by one‐pot five‐component reaction of 2 equiv of aldehydes 1 , 2 equiv of amines 2 , and 1 equiv of methyl acetoacetate 3 in EtOH at room temperature in good to high yields and short reaction time. The presented methodology offers several advantages such as easy work‐up procedure, reusability of the magnetic nanocatalyst, operational simplicity, green synthesis avoiding toxic reagents and solvent, mild reaction conditions, and no tedious column chromatographic separation.     

Single Crystal to Single Crystal (SC‐to‐SC) Transformation from a Nonporous to Porous Metal–Organic Framework and Its Application Potential in Gas Adsorption and Suzuki Coupling Reaction through Postmodification

A new amino‐functionalized strontium–carboxylate‐based metal–organic framework (MOF) has been synthesized that undergoes single crystal to single crystal (SC‐to‐SC) transformation upon desolvation. Both structures have been characterized by single‐crystal X‐ray analysis. The desolvated structure shows an interesting 3D porous structure with pendent ?NH₂ groups inside the pore wall, whereas the solvated compound possesses a nonporous structure with DMF molecules on the metal centers. The amino group was postmodified through Schiff base condensation by pyridine‐2‐carboxaldehyde and palladium was anchored on that site. The modified framework has been utilized for the Suzuki cross‐coupling reaction. The compound shows high activity towards the C?C cross‐coupling reaction with good yields and turnover frequencies. Gas adsorption studies showed that the desolvated compound had permanent porosity and was microporous in nature with a BET surface area of 2052 m² g^?1. The material also possesses good CO₂ (8 wt %) and H₂ (1.87 wt %) adsorption capabilities.     

Applications of iron and nickel immobilized on hydroxyapatite‐core‐shell γ‐Fe2O3 as a nanomagnetic catalyst for the chemoselective oxidation of sulfides to sulfoxides under solvent‐free conditions

In the present study, Fe²⁺ and Ni²⁺ immobilized on hydroxyapatite‐core‐shell γ‐Fe₂O₃ (γ‐Fe₂O₃@HAp‐Fe²⁺ and γ‐Fe₂O₃@HAp‐Ni²⁺) with a high surface area has been synthesized and characterized by Fourier transform infrared (FTIR), X‐ray diffraction (XRD), vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), and scanning electron microscope (SEM) techniques. Then, γ‐Fe₂O₃@HAp‐Fe²⁺ and γ‐Fe₂O₃@HAp‐Ni²⁺ were used as a new and magnetically recoverable nano catalyst for the selective oxidation of sulfides to sulfoxides with 33% aqueous H₂O₂ (0.5 mL) as an oxidant at room temperature in good to excellent yields and short reaction time. Nontoxicity of reagent, mild reaction condition, inexpensive and high catalytic activity, simple experimental procedure, short period of conversion and excellent yields, and ease of recovery from the reaction mixture using an external magnet are the advantages of the present method.     

Electrocatalysis of N2 to NH3 by HKUST‐1 with High NH3 Yield

Electrolytic ammonia synthesis from nitrogen at ambient conditions is appearing as a promising alternative to the Haber‐Bosch process which is consuming high energy and emitting CO₂. Here, a typical MOF material, HKUST‐1 (Cu?BTC, BTC=benzene‐1,3,5‐tricarboxylate), was selected as an electrocatalyst for the reaction of converting N₂ to NH₃ under ambient conditions. At ?0.75 V vs. reversible hydrogen electrode, it achieves excellent catalytic performance in the electrochemical synthesis of ammonia with high NH₃ yield (46.63 μg h^?1 mg^?1 _cat. or 4.66 μg h^?1 cm^?2) and good Faraday efficiency (2.45%). It is indicated that the good performance of the HKUST‐1 catalyst may originate from the formation of Cu(I). In addition, the catalyst also has good selectivity for N₂ to NH₃.     

A Simple Homoleptic Gallium(I) Olefin Complex: Mimicking Transition‐Metal Chemistry at a Main‐Group Metal?

The earth‐metal olefin complex [Ga ^I (COD)₂]⁺[Al(OR^F)₄]^? (COD=1,5‐cyclooctadiene; R^F=C(CF₃)₃) constitutes the first homoleptic olefin complex of any main‐group metal accessible as a bulk compound. It is straight forward to prepare in good yield and constitutes an olefin complex of a main‐group metal that—similar to many transition‐metals—may adopt the +1 and +3 oxidation states opening potential applications. Crystallographic‐, vibrational‐ and computational investigations give an insight to the atypical bonding between an olefin and a main‐group metal. They are compared to classical transition‐metal relatives.     

Transesterification Kinetics Investigation of R‐Substituted Phenyl Benzoates with 4‐Methoxyphenol in the Presence of K2CO3 in DMF

Transesterification of R‐substituted phenyl benzoates 1–5 with 4‐methoxyphenol 6 was kinetically investigated in the presence of K₂CO₃ in dimethylformamide (DMF) at various temperatures. The Hammett plots for the reactions of the 1–5 demonstrate good linear correlations with σ⁰ constants. Low magnitude of ρ_LG values indicate that the leaving group departure occurs after the rate‐determining step. The Brønsted coefficient values for the reactions (?0.2, ?0.16, ?0.13 at 15, 24, 36°C, respectively) demonstrate the weak effect of leaving group substituent on the reactivity of R‐substituted phenyl benzoates 1–5 for the reactions with 4‐methoxyphenol 6 in the presence of K₂CO₃ in DMF. The leaving group substituent effect on free energy (ΔG^≠), enthalpy (ΔH^≠), and entropy (ΔS^≠) of activation was examined. It was shown that the activation parameters obtained depend weakly on the leaving group substituent effect. The reaction is entropy controlled in case the leaving group substituent becomes electron withdrawing.     

Ab initio study of the insertion reactions of Sc+(1D) with HF,HCl, H2O,H2S,NH3, PH3, CH4, and SiH4

The mechanism of scandium cation Sc⁺(¹D) insertion into HF, HCl, H₂O, H₂S, NH₃, PH₃, CH₄, and SiH₄ has been investigated by ab initio molecular theory. All these reactions involve the initial formation of intermediate complexes followed by an H‐atom migration process via a transition state to insertion products. The Sc⁺(¹D) insertion into eight compound reactions indicate that (i) the reaction with hydride of the right‐hand group is more exothermic than that of the left‐hand group and has a lower barrier, and (ii) the reaction with the second‐row hydride has a lower overall barrier and is less exothermic than with the first‐row hydride. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Synthesis of 5‐Aryl‐3‐(methylsulfanyl)‐1H‐pyrazoles via Three‐Component Reaction of 1,1‐Bis(methylsulfanyl)‐2‐nitroethene,Aromatic Aldehydes,and Hydrazine

An efficient approach for the preparation of functionalized 5‐aryl‐3‐(methylsulfanyl)‐1H‐pyrazoles 2 is described. This three‐component reaction between benzaldehydes 1 , NH₂NH₂?H₂O, and 1,1‐bis(methylsulfanyl)‐2‐nitroethene proceeds in EtOH under reflux conditions in good‐to‐excellent yields. The structures of 2 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS). A plausible mechanism for this type of reaction is proposed (Scheme 2).     

Modified Riemschneider Reaction of 3‐Thiocyanatoquinolinediones

The Riemschneider reaction of 3‐thiocyanatoquinoline‐2,4(1H,3H)‐diones with conc. H₂SO₄ was investigated. Using different reaction conditions, 13 types of reaction products were isolated. Compounds bearing a Me, Et, or Bu group at C(3) afforded mainly [1,3]thiazolo[5,4‐c]quinoline‐2,4‐diones and 1,9b‐dihydro‐9b‐hydroxythiazolo[5,4‐c]quinoline‐2,4‐diones. In the case of the 3‐Bu derivatives of the starting compounds, C‐debutylation was also observed. If a Bn group is present at C(3), rapid C‐debenzylation of the starting thiocyanates occurred, yielding [1,3]oxathiolo[4,5‐c]quinoline‐2,4‐diones, and mixtures of mono‐, di‐, and trisulfides derived from 4‐hydroxy‐3‐sulfanylquinoline‐2‐ones. The reaction mechanism of all of the transformations is discussed. All new compounds were characterized by IR, ¹H‐ and ¹³C‐NMR, and EI and ESI mass spectra, and in some cases, ¹⁵N‐NMR spectra were also used to characterize new compounds.     

Selective synthesis of (3‐ferrocenylprop‐2‐en‐1‐yl)triphenylphosphonium iodide: crystal structure determination of two polymorphs

This work is part of a project studying the reactivity of a new ferrocenyl allylammonium salt, [3‐(trimethylazaniumyl)prop‐1‐en‐1‐yl]ferrocene iodide, (1⁺)·I⁻, with different nucleophiles. With nitrogen‐based nucleophiles, different ferrocenyl allylamine isomers have been synthesized successfully in good yield. Optimization of the basicity of the reaction medium has allowed selection of the best operating conditions to obtain the targeted isomer. In a similar way and in order to introduce phosphorus‐containing functional groups, the reaction of ammonium salt (1⁺)·I⁻ with a phosphorus nucleophile, namely triphenylphosphane, was attempted. It was then possible to isolate single crystals of (3‐ferrocenylprop‐2‐en‐1‐yl)triphenylphosphonium iodide, [Fe(C₅H₅)(C₂₆H₂₃P)]I, which is shown to crystallize in two concomitant polymorphic forms, viz. a triclinic form, (I), in the space group P , and a monoclinic form, (II), in the space group P 2₁/c . In the inter‐ion packing of polymorph (I), the cations form bilayer ribbons via C—H…π and π–π stacking interactions. In polymorph (II), where π–π interactions do not occur, adjacent molecules are joined by C—H…π interactions into a one‐dimensional helical arrangement along the b axis.     

Gutmann's Donor Numbers Correctly Assess the Effect of the Solvent on the Kinetics of SNAr Reactions in Ionic Liquids

We report an experimental study on the effect of solvents on the model S_NAr reaction between 1‐chloro‐2,4‐dinitrobenzene and morpholine in a series of pure ionic liquids (IL). A significant catalytic effect is observed with reference to the same reaction run in water, acetonitrile, and other conventional solvents. The series of IL considered include the anions, NTf₂^?, DCN^?, SCN^?, CF₃SO₃^?, PF₆^?, and FAP^? with the series of cations 1‐butyl‐3‐methyl‐imidazolium ([BMIM]⁺), 1‐ethyl‐3‐methyl‐imidazolium ([EMIM]⁺), 1‐butyl‐2,3‐dimethyl‐imidazolium ([BM₂IM]⁺), and 1‐butyl‐1‐methyl‐pyrrolidinium ([BMPyr]⁺). The observed solvent effects can be attributed to an “anion effect”. The anion effect appears related to the anion size (polarizability) and their hydrogen‐bonding (HB) abilities to the substrate. These results have been confirmed by performing a comparison of the rate constants with Gutmann's donicity numbers (DNs). The good correlation between rate constants and DN emphasizes the major role of charge transfer from the anion to the substrate.     

Palladium‐Catalyzed Arylation of Arylboronic Acids with Yagupolskii–Umemoto Reagents

A Pd‐catalyzed Suzuki cross‐coupling of arylboronic acids with Yagupolskii–Umemoto reagents was explored. In contrary to trifluoromethylations, the Pd‐catalyzed reaction of R?B(OH)₂ and [Ar₂SCF₃]⁺[OTf]^? provided the arylation products (R?Ar) in good to high yields. The reaction confirms that the S?Ar bonds of [Ar₂SCF₃]⁺[OTf]^? can be readily cleaved in the presence of Pd complexes. The relatively electron‐poor aryl groups of asymmetric [Ar¹Ar²SCF₃]⁺[OTf]^? salts are more favorably transferred compared to the electron‐rich ones. This reaction represents the first report of utilization of [Ar₂SCF₃]⁺[OTf]^? as arylation reagents in organic synthesis.