Protonation of amino and hydroxypyrimidines. NMR-spectra and structures of mono and dications

Proton-NMR. spectra of amino- and hydroxypyrimidines including biologically important bases have been measured in four solvents: CF₃COOH, CF₃COOH? SO₂, FSO₃H and FSO₃H? SbF₅–SO₂ at 27° and ?55°C. In CF₃COOH mono-cations are formed, whereas in FSO₃H and FSO₃H? SbF₅–SO₂ double protonation occurs. In each case the structures of the protonated species are derived from the chemical shifts of CH, NH and OH protons and proton-proton spin coupling constants. A combination of the measurements described leads to a complete assignment of all proton resonances of the protonated pyrimidines. This approach is also recommended for the structural determination of heterocyclic compounds.     

Rearrangements Involving C8H8F-Cations of the Cage Type

The homo-l, 4 adduct obtained from difluorocarbene and bicyclo [2.2.1]hepta-2, 5-diene ( 1 ) was treated successively with HCl, FSO₃H and SbF₅ in SO₂ClF at low temperature. The protic acids underwent electrophilic addition to the cyclopropane part of 1 , giving the corresponding derivatives. However, in FSO₃H at ? 50°, protonation of the gem-difluoro grouping also occurred to give the 2-fluoro-6-fluorosulfonylbicyclo [3.2.1]oct-2-en-3-yl cation. The reaction of 1 with SbF₅ at ?78° led initially to the formation of the 2-fluorobicyclo [3.2.1 ]octa-2, 6-dien-4-yl cation, which rearranged to 4-fluorotricyclo [5.1.0.0^5,8]oct-3-en-2-yl cation at ?40°. These rearrangements are discussed in the light of those expected for C₈H₈F square pyramidal cations.     

Protonization of purine, adenine, and guanine. NMR spectra and structure of mono, di, and tri cations

Proton NMR. spectra of purine, adenine, guanine and methylsubstituted guanines have been measured in CF₃COOH, FSO₃H and FSO₃H? SbF₅? SO₂ at 27° and low temperatures. These conditions permit to study multiple protonation of purines, using chemical shifts of CH, NH and OH protons. The spectra of mono-, di- and tri-cations are described and fully assigned.     

The protonation of ortho-methoxy- and hydroxy-benzaldehydes in FSO3H?SbF5?SO2 solution

The protonation of o-methoxy- and o-hydroxy-benzaldehydes in FSO₃H? SbF₅? SO₂ solution was investigated by ¹H NMR spectroscopy. The formation of the Z-carbonyl protonated molecule is explained by intramolecular hydrogen bonding.     

Aromatic protonation—part 2 : 1H NMR parameters of the anthracenium ions of some 9-alkyl-, 9-alkyl-α-chloro-, 9,10-dialkyl-anthracenes and 1-chloroanthracene. study on the sit

Seventeen 9-alkylanthracenes (1–17) and 1-chloroanthracene have been protonated with FSO₃H in SO₂CIF as cosolvent at ?78°. For all substrates C(10) protonation was observed, but with some substrates in addition C(9) protonation, if that would lead to relief of steric strain between the substituent at C(9) and the substituent(s) at C(1) [and C(8)]. The C(9) protonated ions exist in the preferred conformation IIa. The ions resulting on ipso-protonation of the 9,10-dialkyl-anthracenes have a similar type of conformation. Based both on this preferred conformation and the peri-chloro effects of the anthracenium ions, it is concluded that these ions are best represented by the equilibirum IIa ? IIb.     

Oxo(trisyl)boran (Me3Si)3C?BO als Zwischenstufe

Oxo(trisyl)borane (Me₃Si)₃C? B?O as an Intermediate The acyclic trisylboranes R? B(OSiMe₃)? Cl ( 4 a ) and R? B(OH)? H ( 5 a ) and the cyclic boranes (? RB? O? CO? CO? O? ) ( 1 a ) and (? RB? O? RB? O? SO₂? O? ) ( 6 a ) [R = (Me₃Si)₃C, “Trisyl”] are thermolyzed in the gasphase to give well-defined products. The tris(trisyl)boroxine (? RB? O? )₃ ( 2 a ) is formed from 4 a and 5 a at 140 and 160°C, respectively, besides Me₃SiCl and H₂, respectively, whereas the six-membered ring [? BMe? CH(SiMe₃)? SiMe₂? O? SiMe₂? CH₂? ] ( 8 ) is the product from 1 a and 6 a at 600 and 700°C, respectively, besides CO/CO₂ and SO₃, respectively. The oxoborane R? B?O is presumably a common intermediate. It is stabilized at the lower temperature by cyclotrimerization to give 2 and at the higher temperature by a sequence of several intramolecular steps: a 1,3-silyl shift along the chain C? B? O, an exchange of Me and Me₃SiO along the chain Si? C? B, and a C? H addition to the B?C double bond; the steps can be rationalized by analogous known reactions. The gas-phase thermolysis at 600°C of the dioxaboracyclohexenes (? BR? O? CR′ = CH? CRR′? O? ) ( 7 b? d ; R = Me, iPr, tBu; R′ = Me) yields the boroxines (RBO)₃ and the enones Me? CO? CH?CHR? Me; the cyclohexene 7 e (R = Me; R′ = CF₃) is not decomposed at 600°C.     

Aromatic protonation—4: On the 1H-2H exchange of three 9-n-alkylanthracenes on reaction with CF3CO2[2H] and FSO3[2H]

The reactions of 9-methyl-, 9-ethyl- and 9-propyl-anthracene with CF₃CO₂[²H] in C[²H]Cl₃ and with FSO₃[²H] in SO₂ClF have been investigated. Using 4 equivalents of CF₃CO₂[²H] at 50° ¹H-²H exchange was observed only for the 10-H and the side-chain α-hydrogens, and on using 8 and 12 equivalents at 50° also for the aromatic α-hydrogens. Treatment of the substrates with FSO₃[²H] at -60° leads to the stable 9-alkyl-[10-²H]-10-anthracenium ions. On warming up to ?25° a slow ¹H-²H exchange of only the 10-¹H of these anthracenium ions is observed. A mechanism for the ¹H-²H exchange of the aromatic and the side-chain α-hydrogens of the 9-alkylanthracenes is presented.     

Aromatic protonation.—3: 1H NMR parameters of some methyl substituted anthracenium ions. Study on the site of protonation

1-Methylanthracene (1-MeA), 2-MeA, 1,2-Me₂A, 1,3-Me₂A, 1,4 Me₂A, 2,3-Me₂A, 1,4,9-Me₃A and 2,3,6,7-Me₄A have been protonated with FSO₃H in SO₂CIF as cosolvent at ?78°. With all substrates C(10)- and/or C(9)-protonation was observed. The site of protonation of the hydrocarbons was found to depend on (i) the degree of mesomeric stabilisation of the positive charge of the resulting anthracenium ions by the Me substituents, and (ii) the relief of steric strain between H(9) and the peri-Me substituent at position 1 on protonation at C(9).     

Polysulfonylamine. LXXII [1]. Triphenylcarbenium- und Triphenylphosphonium-di(fluorsulfonyl)amid: Zwei Kristallstrukturen mit geordneten (FSO2)2N⊖-Lagen

Polysulfonyl Amines. LXXII. Triphenylcarbenium and Triphenylphosphonium Di(fluorosulfonyl)amides: Two Crystal Structures with Ordered (FSO₂)₂N^? Sites Treatment of HN(SO₂F)₂ in CH₂Cl₂ with Ph₃P, Ph₃PO or collidine (=B) affords the compounds Ph₃PH^⊕[(FSO₂)₂N]^? ( 3 ), Ph₃PO · HN(SO₂F)₂, and BH^⊕[(FSO₂)₂N]^? ( 7 ). The carbenium salt Ph₃C^⊕[(FSO₂)₂N]^? ( 5 ), obtained by metathesis of Ph₃CBr with [(C₆H₆)AgN(SO₂F)₂] in CH₂Cl₂, crystallizes from chloroform/petroleum ether as a monosolvate Ph₃C^⊕[(FSO₂)₂N]^? · CHCl₃ ( 6 ). In presence of a sterically hindered base, viz. collidine, 5 is a suitable reagent for the tritylation of molecules containing weakly activated H atoms (e. g.: MeCN → Ph₃CCH₂CN, acetone → tritylacetone; co-product: 7 ). The crystal structures of the ionic solids 3 (monoclinic, space group P2₁/n) and 6 (monoclinic, P2₁/c) were determined by X-ray diffraction at ?130°C; the structure refinements were not impaired by the notorious tendency of the (FSO₂)₂N moiety towards crystallographic disorder. As in the known structure of the tetraphenylarsonium salt, the anion of 3 and 6 adopts a staggered conformation of approximately C₂ symmetry (averages of all values: S? N? S 121.4°, N? S 156.2, S? O 141.6, S? F 156.6 pm). The crystal packing of 6 displays a three-centre C? H(…?O)₂ hydrogen bond between the CHCl₃ molecule and two oxygen atoms of a single anion, resulting in a six-membered ring [R₁²(6) pattern; H …? O 234 and 262 pm]. The crystal of 3 contains one-dimensional arrays of alternating cations and anions connected by a three-centre P? H(…?O)₂ bond [C(6) pattern; H …? O 237 and 254 pm]. The Ph₃C^⊕ cation of 6 is propeller-shaped, with three coplanar central bonds (mean C? C 144.5 pm) and interplanar angles of 52.7, 56.4 and 60.1° between the phenyl groups.     

Unambiguous Proof for Alcoxycarbonyl-group Migration in Wagner-Meerwein Rearrangements

In HSO₃F/SO₂ClF the β-hydroxy esters Ph-CHOH-CMe₂-COOR ( 1 , R?Me, Et) are doubly protonated, then transformed into the fluorosulfates 7 and (partly) into the fluorides 8. At ?15°, both 7 and 8 undergo a rearrangement, forming derivatives of Me₂C?C(Ph)COOR ( 2 ). By labelling 1 with ¹³C, singly (¹³C(3)) and doubly (¹³C(1,3)), it could be shown that exclusively the ROOC groups undergo a 1,2-shift. Compound 2 is also formed in HSO₃F/SO₂ClF from the isomeric Me₂COH-CHPh-COOR ( 3 ) by elimination, and less easily from the α-hydroxy ester Ph-CMe₂-CHOH-COOR (5) via a phenyl 1,2-shift. Another isomer, Ph-C(OH)Me-CHMe-COOR (4) gives products different from 2 . Using more acidic systems containing SbF₅, the free carbenium ions 13 (Ph-CH⁺-CMe₂-COOR) can be stabilized; they do not form 2 , possibly because of complexation of the ester group with SbF₅. The energy profile and the mechanism of the rearrangement 1 → 2 are discussed.     

L'hydrolyse acide des diazocétones alcoylées: Formation d'ions α-acylcarbonium secondaires

Hydrolysis of secondary diazoketones CH₃? CO? CN₂? R (R ? Me, Et, isopropyl) by aqueous perchloric acid is characterized by rate-determining protonation demonstrated by solvent isotope effects kD₂O/kH₂O = 0,4–0,6 and by the intervention of general acid catalysis. The product determining step, yielding keto-alcohols and keto-olefines, is independent of added nucleophiles; this is interpreted as resulting from the intermediate formation of (more or less free) αhyphen;ketocarbonium is ions. The hydride shift observed wih III (R = isopropyl) supports this interpretation. The difference between hydrolysis of primary and of secondary diazoketones is discussed.     

Hydrate der Fluorsulfonsäure: Das Schmelzdiagramm des Systems FSO3H?H2O und die Kristallstruktur des Monohydrats, (H3O)FSO3

Hydrates of Fluorosulfuric Acid: The Melting Diagram of the System FSO₃H? H₂O and the Crystal Structure of the Monohydrate, (H₃O)FSO₃ The system FSO₃H? H₂O has been investigated by difference thermal analysis. By adhering to exclusively lower temperatures in the course of preparation and manipulation of the measuring samples, it was possible to avoid hydrolysis of the S? F bond and to obtain a quasi-binary melting diagram. This reveals the existence of four crystalline hydrates FSO₃H · nH₂O with n = 1, 2, 3, and 4, melting at –12, –53 (dec.), –46, and ?63°C (dec.), respectively. The structure of the monohydrate has been determined (crystal system orthorhombic, space group Pnma, Z = 4 formula units per unit cell; lattice constants a = 8.055, b = 6.465, c = 7.459 Å at ?50°C; final R value with 515 independent observed MoKα diffractometer data at 0.043). The result is a typical oxonium salt, (H₃O)FSO₃, characterized by strong hydrogen bonds only of the kind O? H…?O and with interesting relations to the isosteric, dimorphic compound (H₃O)ClO₄.     

Superacid polymers: Synthesis and analysis of AlCl3–sulfonic acid resin complexes

Crosslinked poly(styrenesulfonic acid) beads in contact with AlCl₃ vapors at 115°C reacted to give HCl and a complex incorporating S, Al, and Cl in the ratio 2:1:2. Electron microprobe x-ray analysis showed that the complexes were distributed uniformly throughout the polymer structure, which consisted of 200 Å microspheres surrounded by a labyrinth of pores. The polymer is a very strong proton donor, comparable to the superacid solution SbF₅ + FSO₃H. Its structural and acidic properties are inferred to be similar to those of the complex formed from AlCl₃ and H₂SO₄.     

Organometallic chemistry : V. Protonation of acylferrocenes under stable ion conditions in fso3h-so2c1f solution

Protonation of acylferrocenes (FeCOR) in FSO₃H-SO₂CIF(SO₂) solution was studied by PMR spectroscopy. The site of protonation is found to be at the carbonyl oxygen atom. Temperature dependent PMR spectra of protonated acylferrocenes FeCROH⁺ (R = CH₃, C₂H₅, C₆H₅, OCH₃) were observed indicating intermolecular hydrogen exchange with the acid solvent system. In addition the PMR spectra of acylferrocenes in FSO₃ H-SO₂ CIF(SO₂) were found to be dependent upon the acid concentration.     

Trifluoroethylene Sultone: Structure and Chemistry

The gas phase structure of trifluoroethylene sultone, ( 1 ) (3,4,4-trifluoro-1,2-oxathietane-2,2-dioxide) was determined by gas electron diffraction, and the four-membered ring was found to be planar. The following ring parameters (r_a distances and ∠_α angles with 3σ uncertainties) were derived in the electron diffraction analysis: C? O = 1.41 Å (ass.), C? C = 1.541(18) Å, S? O = 1.652(5) Å, S? C = 1.822(8) Å, S? C? C = 86.2(15)°, C? C? O = 97.1(28)°, C? O? S = 97.5(21)°, and O? S? C = 79.1(8)°. New spectral data (IR, NMR) of 1 , its acyclic isomer FSO₂CFHC(O)F ( 2 ), and the related anhydride, FSO₂OSO₂CFHC(O)F ( 3 ), are reported. New esters containing the fluorosulfonyl function, FSO₂CFHC(O)OCH₂CF₃ ( 4 ), FSO₂CFHC(O)OCH₂CH = CH₂ ( 5 ), and (FSO₂CFHC(O)OCH₂CH? CH₂? )_n ( 6 ) have been prepared and characterized.     

The Protonation of HSO3F: Preparation and Characterization of Fluorodihydroxyoxosulfonium Hexafluoroantimonate [H2SO3F]+[SbF6]−

Sulfurtrioxide reacts with the superacidic solutions XF/SbF₅ (X=H, D) to form the corresponding salts [X₂SO₃F]⁺[SbF₆]^?, which are the protonated forms of fluorosulfuric acid. The salts have been characterized by vibrational spectroscopy and a single‐crystal structure analysis. [H₂SO₃F]⁺[SbF₆]^? crystallizes in the monoclinic space group P2₁/n (no. 14) with four formula units in the unit cell. The crystal structure possesses a distorted tetrahedral O₃SF skeleton of the cations, which are linked with two strong hydrogen bridges to [SbF₆]^? anions and forms a one‐dimensional chain. The crystal structure and the vibrational spectra are compared to the quantum‐chemical‐calculated free [H₂SO₃F]⁺ cation. Additionally, an [H₂SO₃F(HF)₂]⁺ unit was calculated at the RHF/6‐311⁺⁺G(d,p) level to simulate H???F hydrogen bridges found in the solid state.     

Protonation of Nitramines: Where Does the Proton Go?

The reactions of nitramine, N ‐methyl nitramine, and N ,N ‐dimethyl nitramine with anhydrous HF and the superacids HF/MF₅ (M=As, Sb) were investigated at temperatures below −40 °C. In solution, exclusive O‐protonation was observed by multinuclear NMR spectroscopy. Whereas no solid product could be isolated from the neat HF solutions even at −78 °C, in the HF/MF₅ systems, protonated nitramine MF₆⁻ salts were isolated for the first time as moisture‐sensitive solids that decompose at temperatures above −40 °C. In the solid state, depending on the counterion, O‐protonated or N‐protonated cations can be formed, in accord with theoretical calculations which show that the energy differences between O‐protonation and N‐protonation are very small. The salts [H₂N‐NO₂H][AsF₆], [H₃N‐NO₂][SbF₆], [MeHNNO₂H][SbF₆], and [Me₂NNO₂H][SbF₆] were characterized by their X‐ray crystal structures.     

Synthesis and Study of Cationic,Two‐Coordinate Triphenylphosphine– Gold–π Complexes

Cationic, two‐coordinate triphenylphosphine–gold(I)–π complexes of the form [(PPh₃)Au(π ligand)]⁺ SbF₆^? (π ligand=4‐methylstyrene, 1? SbF₆), 2‐methyl‐2‐butene ( 3? SbF₆), 3‐hexyne ( 6? SbF₆), 1,3‐cyclohexadiene ( 7? SbF₆), 3‐methyl‐1,2‐butadiene ( 8? SbF₆), and 1,7‐diphenyl‐3,4‐heptadiene ( 10? SbF₆) were generated in situ from reaction of [(PPh₃)AuCl], AgSbF₆, and π ligand at ?78 °C and were characterized by low‐temperature, multinuclear NMR spectroscopy without isolation. The π ligands of these complexes were both weakly bound and kinetically labile and underwent facile intermolecular exchange with free ligand (ΔG^≠≈9 kcal mol^?1 in the case of 6? SbF₆) and competitive displacement by weak σ donors, such as trifluoromethane sulfonate. Triphenylphosphine–gold(I)–π complexes were thermally unstable and decomposed above ?20 °C to form the bis(triphenylphosphine) gold cation [(PPh₃)₂Au]⁺SbF₆^? ( 2? SbF₆).     

Reaktion von Formamid mit Kohlenstoffdisulfid 2. Kristallstruktur von Kalium-N-formyldithiocarbamat [1]

On Chalcogenolates. 148. Reaction of Formamide with Carbon Disulfide. 2. Crystal Structure of Potassium N-Formyl Dithiocarbamate K[S₂C? NH? CO? H] crystallizes with Z = 16 in the monoclinic space group Cc with cell dimensions a = 13.187(13) Å, b = 12.928(3) Å, c = 13.962(6) Å, and β = 101.75 (3)°. The crystal structure has been determined from single crystal X-ray data measured at 20°C and refined to a conventional R of 0.034 for 1857 independent reflections (R_w = 0.038). The compound crystallizes by building a super-structure, which is based on an H-bridged 16-membered ring-system, formed by four[S₂C? NH? CO? H]^? anions. Two different binuclear K⁺ coordination polyhedra are formed with two oxygen and two sulfur atoms in common.     

Über die Gasphasenstruktur von CF3NCl2 und die Darstellung von CF3NCl2F+MF6− (M = As,Sb) und CF2 = NClF+SbF6−

Gas Phase Structure of CF₃NCl₂ and Preparation of CF₃NCl₂F⁺MF₆^? (M = As, Sb) and CF₂ = NCl₂F⁺SbF₆^? The gas phase structure of CF₃NCl₂ is reported. The following skeletal parameters are derived (r_a-values, error limits are 3σ values): N? C = 1.470(6) Å, N? Cl = 1.733(3) Å, ClNCl = 111.5(4)° and ClNC = 107.6(5)°. CF₃NCl₂F⁺MF₆^? is prepared by fluorination of CF₃NCl₂ with XeF⁺MF₆^?. The same educt CF₃NCl₂ reacts with XeF⁺SbF₆^? at ?40°C to CF₂ = NClF⁺SbF₆^? under elimination of ClF.