Aryl Sulfonium Salts for Site‐Selective Late‐Stage Trifluoromethylation

Incorporation of the CF₃ group into arenes has found increasing importance in drug discovery. Herein, we report the first photoredox‐catalyzed cross‐coupling of aryl thianthrenium salts with a copper‐based trifluoromethyl reagent, which enables a site‐selective late‐stage trifluoromethylation of arenes. The reaction proceeds with broad functional group tolerance, even for complex small molecules on gram scale. The method was further extended to produce pentafluoroethylated derivatives.     

5‐(Cyano)dibenzothiophenium Triflate: A Sulfur‐Based Reagent for Electrophilic Cyanation and Cyanocyclizations

The synthesis of 5‐(cyano)dibenzothiophenium triflate 9 , prepared by activation of dibenzo[b,d]thiophene‐5‐oxide with Tf₂O and subsequent reaction with TMSCN is reported, and its reactivity as electrophilic cyanation reagent evaluated. The scalable preparation, easy handling and broad substrate scope of the electrophilic cyanation promoted by 9 , which includes amines, thiols, silyl enol ethers, alkenes, electron rich (hetero)arenes and polyaromatic hydrocarbons, illustrate the synthetic potential of this reagent. Importantly, Lewis acid activation of the reagent is not required for the transfer process. We additionally report herein biomimetic cyanocyclization cascade reactions, which are not promoted by typical electrophilic cyanation reagents, demonstrating the superior ability of 9 to trigger challenging transformations.     

Metal‐Free One‐Pot Synthesis of Benzofurans

Ethyl acetohydroxamate was efficiently arylated with diaryliodonium salts at room temperature under transition‐metal‐free conditions. The obtained O‐arylated products were reacted in situ with ketones under acidic conditions to yield substituted benzo[b]furans through oxime formation, [3,3]‐rearrangement, and cyclization in a fast and operationally simple one‐pot fashion without using excess reagents. Alternatively, the O‐arylated products could be isolated or transformed in situ to aryloxyamines or O‐arylaldoximes. The methodology was applied to the synthesis of Stemofuran A and the formal syntheses of Coumestan, Eupomatenoid 6, and (+)‐machaeriol B.     

One‐Pot Synthesis of 1,3,5‐Triarylpyrazoles

A series of novel 1,3,5‐triarylpyrazoles 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h , 3i , 3j , 3k , 3l , 3m , 3n , 3o , 3p , 3q , 3r , 3s , 3t , 3u , 3v , 3w , 3x were synthesized from flavanones, arylhydrazines, and trimethyl phosphate in an one‐pot procedure. Facile reaction process, easy after‐reaction workshop, and good yields are the distinct characteristics of the developed protocol. The target compounds were characterized by element analysis, infrared ray (IR), ¹H NMR spectra, and electrospray ionization‐mass spectrometry. The structure of representative compound 3h (C₂₃H₂₀N₂O₃, M_r = 372.42) was further confirmed by X‐ray diffraction. It crystallizes in monoclinic, space group P 2₁/c, a = 8.9720(5), b = 24.5523(13), c = 8.9687(6) Å, α = 90.0000, β = 102.6417(17), γ = 90.0000°, V = 1927.76(20) ų, Z = 4, μ(MoKα) = 0.086, F(000) = 784, D_c = 1.283 g/cm³, the final R = 0.0349 and wR = 0.0844 for 1668 observed reflections (I > 2σ(I))     

One‐Pot Sequence‐Controlled Synthesis of Oligosiloxanes

Silicones (organopolysiloxanes) have found applications in a wide range of research areas, and their unique and valuable properties have rendered these materials virtually irreplaceable. Despite the fact that silicones have been employed industrially for more than 70 years, synthetic routes to generate silicones remain limited, and the sequence‐controlled synthesis of oligo‐ and polysiloxanes still represents a major challenge in silicone chemistry. Described here is a highly selective sequence‐controlled synthesis of linear, branched, and cyclic oligosiloxanes by simple iteration of two reactions, specifically, a B(C₆F₅)₃‐catalyzed dehydrocarbonative cross‐coupling of alkoxysilanes with hydrosilanes and a B(C₆F₅)₃‐catalyzed hydrosilylation of carbonyl compounds, in a single flask. The sequence of the resulting oligosiloxanes can be controlled precisely by the order of addition of the hydrosilane monomers.     

One‐Pot C−H Functionalization of Arenes by Diaryliodonium Salts

A transition‐metal‐free, mild, and highly regioselective synthesis of nitroarenes from arenes has been developed. The products are obtained in a sequential one‐pot reaction by nitration of iodine(III) reagents with two carbon ligands, which are formed in situ from iodine(I). This novel concept has been extended to formation of aryl azides, and constitutes an important step towards catalytic reactions with these hypervalent iodine reagents. An efficient nitration of isolated diaryliodonium salts has also been developed, and the mechanism is proposed to proceed by a [2,2] ligand coupling pathway.     

Metal‐Assisted One‐Pot Synthesis of Isoporphyrin Complexes

Zinc and cadmium complexes of meso‐arylisoporphyrins carrying a pyrrolyl or dipyrrinyl substituent at the sp³ carbon atom were obtained through a simple one‐pot variation of the Alder–Longo porphyrin synthesis. Key to the formation and stabilization of isoporphyrins is the presence of metal acetates during the oxidative macrocyclization step. The characteristic Q‐bands of isoporphyrins are found in the NIR region between 750 nm and 880 nm. All of the isolated pyrrolyl‐ and dipyrrinyl‐appended isoporphyrins are stable under typical laboratory conditions and allow chemical transformations like BF₂ coordination, transmetalation, and ligand exchange.     

One‐Pot Four‐Component Synthesis of Tetrasubstituted Pyrroles

A convenient one‐pot four‐component synthesis of tetrasubstituted pyrroles was carried out through the reaction of butane‐2,3‐dione with α‐aminophosphorous ylides, obtained in situ from the 1 : 1 : 1 addition reaction between triphenylphosphine, dialkyl acetylenedicarboxylate, and ammonium acetate.     

One‐Pot Synthesis of Highly Emissive Dipyridinium Dihydrohelicenes

Condensation of a pyridyl‐2‐carbaldehyde derivative with 2‐(bromoethyl)amine hydrobromide gave tetracyclic pyrido[1,2‐a]pyrido[1′,2′:3,4]imidazo‐[2,1‐c]‐6,7‐dihydropyrazinium dications in excellent yields. Crystal structures and NOE data demonstrated the helical character of the dications, the dihedral angles between the two pyrido groups ranging from 28–45°. An intermediate in the synthesis was also characterized. A much brighter emission compared to literature helicenes has been found, with quantum yields as high as 60 % in the range of λ=460–600 nm. Preliminary cytotoxicity studies against HT‐29 cancer cells demonstrated moderate‐to‐good activity, with IC₅₀ values 12–30× that of cisplatin.     

Zirconium/Nickel‐Mediated One‐Pot Ketone Synthesis

A zirconium/nickel‐mediated one‐pot synthesis of ketones is reported. In the presence of Zn or Mn, Cp₂ZrCl₂ was found to dramatically accelerate the coupling and suppress side product formation via an I→SPy displacement at the same time. Unlike Zn/Pd‐ and Fe/Cu‐mediated one‐pot ketone syntheses, the new method is effective for nucleophiles bearing OR or equivalent functional groups at the α‐position. A mechanism comprising a nickel catalytic cycle, a zirconium catalytic cycle, and Zr→Ni transmetalation is proposed, and Cp₂ZrCl₂ and/or low‐valent Zr species are suggested to play crucial dual roles.     

One‐Pot Synthesis of Microcapsules with Nanoscale Inclusions

Temperature responsive poly(N‐isopropylmethacrylamide) (pNIPMAm) microgel capsules around 1 µm containing multiple poly(N‐isopropylacrylamide) (pNIPAm) nanoinclusions were prepared. This structure was achieved through the addition of a cross‐linked pNIPMAm shell to stable, monodispersed aggregates of pNIPAm chains. This one‐pot synthetic approach resulted in core/shell microgels at high temperature wherein only the shell (pNIPMAm) component contained stable, covalent cross‐links between chains. Thus, upon decreasing the temperature following synthesis, the majority of the encapsulated pNIPAm chains escaped from the shell, resulting in nearly hollow microcapsules. Remnant pNIPAm segments in the microcapsule then form nanoparticulate inclusions upon raising the temperature.

     

A Novel One‐Pot Synthesis of Substituted Quinolines

A synthesis of quinoline derivatives is described via reaction between ethyl bromopyruvate (=ethyl 3‐bromo‐2‐oxopropanoate), acetylenedicarboxylate, and isatin (=1H‐indole‐2,3‐dione) in the presence of NaH as a base. Also, these reactions were performed without ethyl bromopyruvate. The reaction in the presence of ethyl bromopyruvate provides regioselectively a quinoline with the ethyl ester group in 4‐position. In the absence of ethyl bromopyruvate, the reaction leads to functionalized quinolines with the same ester groups in 2‐, 3‐, and 4‐positions.