A New Portal to SuFEx Click Chemistry: A Stable Fluorosulfuryl Imidazolium Salt Emerging as an “F−SO2+” Donor of Unprecedented Reactivity,Selectivity, and Scope

Sulfuryl fluoride, SO₂F₂, has been found to derivatize phenols in all kinds of environments, even those in highly functional molecules. We now report that a solid fluorosulfuryl imidazolium triflate salt delivers the same “F?SO₂ + ” fragment to Nu?H acceptor groups in the substrates. However, this triflate salt is a far more reactive fluorosulfurylating agent than SO₂F₂ and displays selectivity preferences of its own. Moreover, the new azolium triflate reagent reacts once with primary amines and anilines before the reaction stops. On the other hand, with triethylamine and two equivalents of the “F?SO₂ + ” donor present, it proceeds on to the bis(fluorosulfuryl)imides in good yield—two important conversions that we have never seen with sulfuryl fluoride as the electrophile.     

A Unified Approach to Couple Aromatic Heteronucleophiles to Azines and Pharmaceuticals

Coupling aromatic heteronucleophiles to arenes is a common way to assemble drug‐like molecules. Many methods operate via nucleophiles intercepting organometallic intermediates, via Pd‐, Cu‐, and Ni‐catalysis, that facilitate carbon‐heteroatom bond formation and a variety of protocols. We present an alternative, unified strategy where phosphonium salts can replicate the behavior of organometallic intermediates. Under a narrow set of reaction conditions, a variety of aromatic heteronucleophile classes can be coupled to pyridines and diazines that are often problematic in metal‐catalyzed couplings, such as where (pseudo)halide precursors are unavailable in complex structures with multiple polar functional groups.     

Enantioselective synthesis of indolo[2,3-b]-dihydrothiopyranones via [3+3] cycloaddition of chiral α,β-unsaturated acylammonium salts

A nucleophile-catalyzed Michael addition/proton transfer/lactonization (NCMPL) organocascade process of chiral α,β-unsaturated acylammonium salts and indoline-2-thiones is described, which delivers the indolo[2,3-b]dihydrothiopyranone motifs in high yields (up to 97%) with good to excellent enantioselectivities (up to 98% ee).     

Access to 3-aminobenzothiophenes and 3-aminothiophenes fused to 5-membered heteroaromatic rings through 6π-electrocyclization reaction of keteniminium salts

We described a general approach to 3-aminobenzothiophenes and 3-aminothiophenes fused to 5-membered heteroaromatic rings as thiophenes, furans and pyrroles through a 6π-elctrocyclization reaction of keteniminium salts. We investigated various substituents not only on the aromatic rings, but also at C-2 and on the nitrogen atom of the keteniminium salt. In particular, we have determined the electronic requirements of the nitrogen substitution to secure the efficient formation of the corresponding keteniminium salt. A clear relation between the pK_a of the amine leading to the formation of the keteniminium salt and the yield obtained for benzothiophene is established and should find broad application to other reactions involving these intermediates. Additional insight on the ease of this 6π-electrocyclization reaction was gained through competition reactions and DFT calculations.     

Recyclable CNT-chitosan nanohybrid film utilized in copper-catalyzed aerobic ipso-hydroxylation of arylboronic acids in aqueous media

A convenient heterogeneous catalytic system consisting of recyclable and reusable carbon nanotube-chitosan nanohybrid film and copper salt was developed for the aerobic ipso-hydroxylation of arylboronic acids. A variety of arylboronic acids bearing electron-withdrawing or electron-donating groups were smoothly transformed at room temperature in water to afford the corresponding phenols in high yields.     

A new class of flexible energetic salts, part 3: The crystal structures of the 3,3-dinitroazetidinium dinitramide and 1-i-propyl-3,3-dinitroazetidinium dinitramide salts

The crystal structures of 3,3-dinitroazetidinium, 1, and 1-i-propyl-3,3-dinitroazetidinium dinitramide, 2, have been determined. 1 crystallizes in the orthorhombic space group Cmc2₁ with cell dimensions a = 9.932(1), b = 8.545(1), c = 11.107(1) Å, while 2 crystallizes in the orthorhombic space group Pbca with cell dimensions a = 11.464(2), b = 11.657(2), c = 17.916(4) Å. Compound 2 formed spontaneously from 1 by reacting with the solvent, acetone, during attempts to recrystallize it. The conformations adopted by the dinitramide ions are quite different with the bend, twist, and torsion angles for the dinitramide ion in 1 being much smaller than those in 2. Possible reasons for the dramatic differences in conformations observed in 1 and 2 are the different local symmetries for this ion found in the two structures as well as the absence of hydrogen bonding interactions in 2.     

Imidazolium chloride organophosphate antidotes

The structures of four imidazolium oxime derivatives were solved by direct methods. These compounds have been shown to be effective in the treatmen of organophosphate poisoning. Despite substantial differences in the nature of the substituent on N1, all four compounds have similar shapes when viewed down the plane of the imidazole ring. The potency of these compounds in the treatment of organophosphate poisoning correlates well with the distance between the imidazole ring and the oxygen moiety on the side chain. 2-(hydroxyimino)methyl-3-methyl-1-[1-(3-methyl-sulfonylpropyloxy) methyl]imidazolium chooride (1) crystallizes in the triclinic space groupPī (Z=2). The unit cell parametersa, b, c (?) and α, β, and γ (^o) were: 8.506(2), 8.787(4), 10.070(4), 73.68(3), 81.37(3), 85.39(3). 2-(hydroxyimino)-methyl-3-methyl-1-(2′-N-phenylsulfonylamino-1′-ethyl) imidazolium chloride (2) crystallizes in the monoclinic space groupP2 ₁ la(Z=4). The unit cell parametersa, b, c (?) and β (^o) were: 12.690(2), 6.317(4), 20.193(4), 91.47(2). 1-(2′-ethyl-2′-trifluoromethanesulfonyl-aminoethyl)-2-(hydroxyimino) methyl-3-methylimidazolium chloride (3) crystallizes in the triclinic space groupPī (Z=2). The unit cell parametersa, b, c (?) and α, β, and γ (^o) were: 6.635(1), 11.333(2), 12.274(3), 115.05(3), 98.46(3), 90.11(3). 2-(hydroxyimino)-methyl-3-methyl-1-[2-(2-methyl-3-nitrobutyloxy) methyl]-imidazolium chloride (4) crystallizes in the orthorhombic space groupP2₁2₁2₁ (Z=4). The unit cell parametersa, b, andc (?) were: 10.034(1), 11.401(2), 13.352(2).     

Catalytic olefination of carbonyl compounds. Effect of the structure of the carbonyl compound on the reaction

The mechanism of the novel reaction of catalytic olefination of carbonyl compounds was studied. The reaction involves the transformation of hydrazones of aromatic aldehydes and ketones into the corresponding dichloroalkenes and symmetrical azines by the treatment with carbon tetrachloride in the presence of CuCl as a catalyst. The stability of intermediate diazoalkanes is the main factor determining the direction of the reaction. In the case of sufficiently stable diazoalkanes, other products can be formed under the reaction conditions along with the products of catalytic olefination.     

Highly active, hexabutylguanidinium salt/zinc bromide binary catalyst for the coupling reaction of carbon dioxide and epoxides

An experimentally simple and inexpensive catalyst system based on hexabutylguanidinium/ZnBr₂ has been developed for the coupling of carbon dioxide and epoxides to form cyclic carbonates with significant catalytic activity under mild reaction conditions without using additional organic solvents (e.g. the turnover frequencies (TOF, h⁻¹) values as high as 6.6 × 10³ h⁻¹ for styrene oxide and 1.01 × 10⁴ h⁻¹ for epichlorohydrin). This catalyst system also offers the advantages of recyclability and reusability. Therefore, it is a very effective, environmentally benign, and simple catalytic process. The special steric and electrophilic characteristics of hexabutylguanidinium bromide ionic liquid result in the prominent performance of this novel catalyst system.