Methyl Triflate Research Articles

Water‐Soluble Photoinitiators from Dimethylamino‐Substituted Monoacylphosphine Oxide for Hydrogel and Latex Preparation

AbstractIn order to respond to the growing demand for radiation‐curable waterborne products like hydrogels or inks, there is a need for water‐soluble radical photoinitiators exhibiting absorption in the near UV to visible range. Herein the synthesis of a novel type‐I diphenylphosphine oxide photoinitiator bearing a 2,6‐dimethyl‐4‐dimethylaminobenzoyl group is described. The presence of a tertiary amino group in the para position of the benzoyl group results in an increased absorption in the visible range and its facile conversion into water‐soluble derivatives after a subsequent protonation or quaternization reaction. Quaternization with methyl triflate (MeOTf) yields a water‐soluble monoacylphosphine oxide compound displaying a quaternary ammonium group N(CH3)3+ OTf−. The main characteristics are water‐solubility, shelf‐stability, absorption in near‐UV range, low cytotoxicity, and efficient α‐scission as evidenced by steady‐state photolysis experiments. Its photopolymerization efficiency has been evaluated by real‐time Fourier transform infrared spectroscopy at 385 and 420 nm using an aqueous solution of poly(ethylene glycol) acrylate. The polymerization rate is comparable to that obtained with the conventional water‐soluble monoacylphosphine oxide TPO‐Li. Using this new photoinitiator, 3D‐printed hydrogels, and aqueous polymer dispersions can be prepared.

Synthesis of 2‐Aryl‐N‐(EWG‐methyl)‐N‐methylpyrrolidinium Salts as Precursors of Ylides Entering the [1,2] Stevens Rearrangement

AbstractN‐(EWG‐CH2)‐N‐methyl‐2‐phenylpyrrolidinium (EWG ‐ electron‐withdrawing group) salts were obtained in two different ways. N‐(EWG‐CH2)‐2‐phenylpyrrolidines were quaternized with iodomethane, dimethylsulfate or methyl trifluoromethanesulfonate forming pyrrolidinium iodides, methylsulfates and triflates. The counterion exchange in the methylsulfates was carried out yielding respective tetrafluoroborates. The second method was based on the quaternization of N‐methyl‐2‐phenylpyrrolidine with methyl α‐halogenoacetate or phenacyl bromide. All listed salts were oily and formed in high yields as mixtures of diastereoisomers, with cis or trans isomer predominating, depending on the method applied. The effect of the counterion present in the obtained salts was analyzed. Ylides generated from these salts in different base/solvent systems afforded products of the [1,2] Stevens rearrangement, 2‐EWG‐1‐methyl‐3‐phenylpiperidines, with the trans isomers predominating, in moderate to good yields. In case of the [1,2] shift, the yields of respective products depended on EWG present in the substrate (methoxycarbonyl, acetyl, dimethylcarbamoyl and benzoyl).

Multistimuli-Responsive Fluorescent Organometallic Assemblies Based on Mesoionic Carbene-Decorated Tetraphenylethene Ligands and Their Applications in Cell Imaging

Multistimuli-Responsive Fluorescent Organometallic Assemblies Based on Mesoionic Carbene-Decorated Tetraphenylethene Ligands and Their Applications in Cell Imaging

Eightfold Electrophilic Methylation of Octacyanotungstate [W(CN)8]4–/3–: Preparation of Homoleptic, Eight-Coordinate Methyl Isocyanide Complexes [W(CNMe)8]4+/5+

Homoleptic eightfold coordinated methyl isocyanide complexes of W(IV) and W(V) have been prepared for the first time. The reaction of [NBu4]4[W(CN)8] with methyl triflate (MeOTf) gives [W(CNMe)8][OTf]4. The even stronger methylating mixture of methyl fluoride (MeF) and arsenic pentafluoride (AsF5) in liquid sulfur dioxide (SO2) is able to fully alkylate both [NBu4]4[W(CN)8] and [NBu4]3[W(CN)8]. The paramagnetic octakis(methyl isocyanide)tungsten(V) complex [W(CNMe)8][AsF6]5 is thermally highly unstable above -30 °C. All compounds have been characterized via single-crystal X-ray diffraction and IR, Raman, and NMR or EPR spectroscopy.

Oxidizing Cerium(IV) Alkoxide Complexes Supported by the Kläui Ligand [Co(η5-C5H5){P(O)(OEt)2}3]-: Synthesis, Structure, and Redox Reactivity.

Tetravalent cerium alkoxide complexes supported by the Kläui tripodal ligand [Co(η5-C5H5){P(O)(OEt)2}3]- (LOEt-) have been synthesized, and their nucleophilic and redox reactivity have been studied. Treatment of the Ce(IV) oxo complex [CeIV(LOEt)2(O)(H2O)]·MeCONH2 (1) with iPrOH or reaction of [CeIV(LOEt)2Cl2] (2) with Ag2O in iPrOH afforded the Ce(IV) dialkoxide complex [CeIV(LOEt)2(OiPr)2] (3-iPr). The methoxide and ethoxide analogues [CeIV(LOEt)2(OR)2] (R = Me (3-Me), Et (3-Et)) have been prepared similarly from 2 and Ag2O in ROH. Reaction of 3-iPr with an equimolar amount of 2 yielded a new Ce(IV) complex that was formulated as the chloro-alkoxide complex [CeIV(LOEt)2(OiPr)Cl] (4). Treatment of 3-iPr with HX and methyl triflate (MeOTf) afforded [Ce(LOEt)2X2] (X- = Cl-, NO3-, PhO-) and [CeIV(LOEt)2(OTf)2], respectively, whereas treatment with excess CO2 in hexane led to isolation of the Ce(IV) carbonate [CeIV(LOEt)2(CO3)]. 3-iPr reacted with water in hexane to give a Ce(III) complex and a Ce(IV) species, presumably the reported tetranuclear oxo cluster [CeIV4(LOEt)4(O)5(OH)2]. The Ce(IV) alkoxide complexes are capable of oxidizing substituted phenols, possibly via a proton-coupled electron transfer pathway. Treatment of 3-iPr with ArOH afforded the Ce(III) aryloxide complexes [CeIII(LOEt)2(OAr)] (Ar = 2,4,6-tri-tert-butylphenyl (5), 2,6-diphenylphenyl (6)). On the other hand, a Ce(III) complex containing a monodeprotonated 2,2'-biphenol ligand, [CeIII(LOEt)2(tBu4C12H4O2H)] (7) (tBu4C12H4O2H2 = 4,4',6,6'-tetra-tert-butyl-2,2'-biphenol), was isolated from the reaction of 3-iPr with 2,4-di-tert-butylphenol. The crystal structures of complexes 3-iPr, 3-Me, 3-Et, and 5-7 have been determined.

Grafting of Poly(2‐Oxazoline) Side Chains from Polyester Containing Oxazoline Units and Their Blends with Water Soluble Vinyl Polymers

AbstractTernary polycondensation of thiomalic acid (TMA), adipic acid (ADA), and 1,5‐pentanediol (PD) at 80 °C proceeds to give polyester having pendent mercapto groups. After the mercapto groups are consumed quantitatively by a Michael addition with 2‐isopropenyl‐2‐oxazoline (IPOx) to create an initiation point for grafting, successive additions of methyl triflate (MeOTf) and 2‐oxazoline allow ring‐opening polymerization of 2‐oxazoline from the IPOx unit to give a graft copolymer with a Mn of 2.2 × 104 ‐ 3.7 × 104 and an molecular dispersity index (Mw/Mn = 1.9–2.6). The synthesized polyester‐based graft copolymer is water‐soluble and forms transparent blend films with poly(vinyl alcohol) (PVA) and poly(N‐isopropy acrylamide) (PNIPAM) using solvent cast methods. Differential scanning calorimetry measurements show that blends with PVA (<30% of the graft copolymer) show a single Tgs over the whole composition range. All scans for the blends with PNIPAM have a single Tgs that is between those of the parent polymers indicating that the graft copolymer shows excellent miscibility with PNIPAM, although the parent polyester, poly(TMA‐alt‐PD)‐co‐poly (ADA‐alt‐PD) does not exhibit such miscibility.

Reaction of Phosphorus Trihalides with Methyl Triflate. Molecular and Supramolecular Structure of Methyltrichloro- and Methyltribromophosphonium Triflates

Prolonged (~4 years) keeping of mixtures of phosphorus trichloride or tribromide with methyl triflate in dark at 20–25°C has led to the formation of crystalline methyltrichloro- and methyltribromophosphonium triflates with a content of 10–11% in the reaction mixture and yield of 5–6%. Structure of the triflates has been elucidated by means of X-ray diffraction analysis.

A Base-Stabilized Silylene-Promoted C(sp3)-H Borylation and H2 Activation.

Treatment of the amidinato amidosilylene [L{(Me3Si)2N}Si:] [1, L = PhC(NtBu)2] with a slight excess of borane-tetrahydrofuran complex [BH3·THF] in toluene at room temperature afforded the silylene-borane adduct [L{(Me3Si)2N}Si:→BH3] (2). A triflate substituent was introduced on the boron center by reacting 2 with methyl triflate [MeOTf] (OTf = OSO2CF3) in toluene at room temperature to form [L{(Me3Si)2N}Si:→BH2OTf] (3), with the elimination of CH4 gas. The intramolecular C(sp3)-H borylation and H2 elimination occurred by reacting complex 3 with 1 in refluxing toluene to form a C-B bond in the resulting silylene-boronium ion 5. Complex 5 activated H2 gas or NH3BH3 at room temperature to form silylene-borane adduct 2 and [L{(Me3Si)2N}Si-H]OTf. Additionally, the reaction of 5 with H2 was studied through density functional theory calculations.

Successive Protonation and Methylation of Bridging Imido and Nitrido Ligands at Titanium Complexes

The reactions of nitrido complexes [{Ti(η5-C5Me5)(μ-NH)}3(μ3-N)] (1) and [{Ti(η5-C5Me5)}4(μ3-N)4] (2) with electrophilic reagents ROTf (R = H, Me; OTf = OSO2CF3) in different molar ratios have allowed the structural characterization of a series of titanium intermediates en route to the formation of the ammonium salts [NR4]OTf and [NR4][Ti(η5-C5Me5)(OTf)4]. The treatment of the trinuclear imido-nitrido complex 1 with 5.5 equiv of triflic acid in toluene at room temperature led to the dinuclear complex [Ti2(η5-C5Me5)2(μ-N)(NH3)(μ-O2SOCF3)2(OTf)] (3) and [NH4]OTf. Compound 3, along with the ammonium salts [NMe4]OTf and [NMe4][Ti(η5-C5Me5)(OTf)4] (5), was also obtained in the reaction of 1 with 8 equiv of methyl triflate in toluene at 100 °C. The trinuclear complex [Ti3(η5-C5Me5)3(μ-N)(μ-NH)2(μ-O2SOCF3)(OTf)] (4), an intermediate in the formation of 3, was isolated in the treatment of 1 with 4 equiv of MeOTf, although compound 4 was prepared in better yield by treatment of 1 with Me3SiOTf (2 equiv). Addition of a large excess of MeOTf or HOTf reagents to solutions of 3 resulted in the clean formation of ammonium salts [NR4][Ti(η5-C5Me5)(OTf)4] (R = Me (5), H (6)). Treatment of the tetranuclear nitrido complex [{Ti(η5-C5Me5)}4(μ3-N)4] (2) with 1 equiv of ROTf in toluene afforded the precipitation of the ionic compounds [{Ti(η5-C5Me5)}4(μ3-N)3(μ3-NR)][OTf] (R = H (8), Me (9)), while a large excess of HOTf led to the formation of [{Ti(η5-C5Me5)}4(μ3-N)3(μ3-NH)][Ti(η5-C5Me5)(OTf)4(NH3)] (10) by rupture of a fraction of tetranuclear molecules. Complex 2 reacted with 1 equiv of [M(η5-C5H5)(CO)3H] (M = Mo, Cr) via hydrogenation of one nitrido ligand to give the molecular derivative [{Ti(η5-C5Me5)}4(μ3-N)3(μ3-NH)] (11) and [{M(η5-C5H5)(CO)3}2], while a second 1 equiv of [M(η5-C5H5)(CO)3H] produced the ionic compounds [{Ti(η5-C5Me5)}4(μ3-N)2(μ3-NH)2][M(η5-C5H5)(CO)3] (M = Mo (12), Cr (13)) by protonation of another nitrido group. The X-ray crystal structures of 3-5, 9, 10, and 13 were determined.

Site-Selective N-Methylation of 5,15-Diazaporphyrins: Reactive Cationic Porphyrinoids that Provide Isoporphyrin Analogues.

N-Alkylation significantly changes the electronic and optical properties, as well as the reactivity of nitrogen-containing π-conjugated molecules. In this study, it is found that treating 5,15-diazaporphyrins with methyl triflate selectively affords the corresponding N-methyl-5,15-diazaporphyrinium cations in good yield. N-Methylation substantially alters the electronic properties and reactivity of diazaporphyrins. The electron-accepting properties of the N-methyl-5,15-diazaporphyrinium cations are enhanced due to their lowered LUMO level. Stabilization of the LUMO energy enables regio- and stereoselective Diels-Alder reactions of the cationic diazaporphyrin with cyclopentadiene. N-Methylation also enhances the acidity of the inner NH protons, and thus, allows facile deprotonation to provide nitrogen-substituted isoporphyrin analogues with only one NH group in the central cavity.

Radiosynthesis of the 11 C-methyl derivative of LBQ657 for PET investigation of the neprilysin inhibitor sacubitril.

Neprilysin, also known as neutral endopeptidase, is a cell surface membrane metalo-endopeptidase that cleaves various peptides. Altered neprilysin expression has been correlated with various cancers and cardiovascular diseases. In this work, we present the radiosynthesis of the novel O-11 C-methylated derivative of LBQ657 (a potent neprilysin inhibitor). (2R,4S)-5-(Biphenyl-4-yl)-4-[(3-carboxypropionyl)amino]-2-methylpentanoic acid [11 C]methyl ester ([11 C]MeOLBQ) is an analog of sacubitril where the alkyl ester is a 11 C-methyl instead of an ethyl. [11 C]MeOLBQ was produced in a one-pot two-step synthesis. The O-11 C-methylation of the pentanoic acid part was done with [11 C]methyl triflate followed by the deprotection of the tert-butyl ester precursor in acidic conditions. [11 C]MeOLBQ ([11 C]7) was produced in 9.5 ± 2.5% RCY (25 ± 6% decay-corrected from [11 C]CO2 , n = 3) high molar activity 348 ± 100 GBq/μmol (9425 ± 2720 mCi/μmol) at EOS, in high chemical (>95%) and radiochemical (>99%) purities. The total synthesis time including HPLC purification and reformulation was 29 minutes. To our knowledge, this is the first PET-labeled analog of the clinically used NEP inhibitor sacubitril.

Synthesis of Pentamethylcyclopentadienyl Dialkynyl Phosphane Iridium(III) complexes. Reactivity of the Complex [Ir(η5-C5Me5)(C≡CPh)2(PPh3)] toward Electrophiles

Dialkynyl iridium(III) complexes [Ir(η5-C5Me5)(C≡CPh)2(PPh2R)] (R = Ph (2a), Me (2b), CH2CH═CH2 (2c)) have been prepared by reaction of the complexes [Ir(η5-C5Me5)Cl2(PPh2R)] (R = Ph (1a), Me (1b), CH2CH═CH2 (1c)) and lithium phenylacetylide. Alternatively, complexes 2a,b have been synthesized by the treatment of the complexes [Ir(η5-C5Me5)I2(PPh2R)] (R = Ph (3a), Me (3b)) with [AgC≡CPh]n. The reactivity of the complex [Ir(η5-C5Me5)(C≡CPh)2(PPh3)] (2a) toward electrophiles is reported. Thus, complex 2a reacts with tetrafluoroboric acid to give the new butenynyl complex [Ir(η5-C5Me5){η3-C(Ph)≡CC═C(H)Ph}(PPh3)][BF4] (4) after stirring for 15 min at room temperature. Complex 4 evolves to [Ir(η5-C5Me5){κ4(P,C,C,C)-PPh2C6H4C(Ph)CHC═C(H)Ph}][BF4] (5) after stirring for 24 h at room temperature. The reaction of complex 2a with methyl trifluoromethanesulfonate leads to the formation of the complex [Ir(η5-C5Me5){κ3(C,C,C)-C6H4C(Me)═C═C═C(H)Ph}(PPh3)][CF3SO3] as a 1:1.5 mixture of the Z (6) and E (7) stereoisomers....

Preparation and Characterization of the Triflate Complex [Cp*(dppe)FeOSO2CF3]: A Convenient Access to Labile Five‐ and Six‐Coordinate Iron(I) and Iron(II) Complexes

Treatment of the iron hydride [Cp*(dppe)FeH] (1) with methyl triflate (CH3OSO2CF3) yielded the iron triflate adduct [Cp*(dppe)FeOSO2CF3] (4, 85 %). In the solid state, the triflate is coordinated at the iron center as shown by XRD (dFe–O = 2.118(4) Å) and IR spectroscopy (νSO = 1305 cm–1). In solution, 4 is in equilibrium with the 16‐electron species [Cp*(dppe)Fe]OSO2CF3 (5(OSO2CF3)), 4/5(OSO2CF3) = 2:1). The CV of 4 displays two waves (E1 = –0.74 V, E2 = 0.24 V vs. SCE) assigned to the [Cp*(dppe)Fe(I)]/[Cp*(dppe)Fe(II)]+ and [Cp*(dppe)Fe(II)]+/[Cp*(dppe)Fe(III)]2+ redox couples. Reduction of 4 with Cp2Co provided the complex [Cp*(dppe)Fe(I)] (6, 95 %) and oxidation of 6 with [Cp2Fe]PF6 gave [Cp*(dppe)Fe]PF6 (5(PF6), 98 %). XRD established the pseudo‐trigonal bipyramidal geometry for the five‐coordinated cation 5+. The reactivity of 5(PF6) and 6 toward small molecules (CH2Cl2, H2O, CO, H2, N2) is reported.

Photoredox Reaction of 2-Mercaptothiazolinium Salts with Silyl Enol Ethers.

A method for the generation of free radicals from thiazolinium salts upon photocatalytic reduction is described. The thiazolinium salts are generated by treatment with methyl triflate of 2-mercaptothiazolines, which can be readily obtained from alkyl bromides and tosylates via a nucleophilic substitution reaction or by hydrothiolation of alkenes. Silyl enol ethers were used to trap the radicals, furnishing ketones after successive single-electron oxidation and elimination of the silyl cation.

Single-base resolution methylome of cotton cytoplasmic male sterility system reveals epigenomic changes in response to high-temperature stress during anther development.

Anther development in flowering plants is highly sensitive to high-temperature (HT) stress. Understanding the potential epigenetic mechanism of anther infertility induced by HT stress in cotton (Gossypium hirsutum L.) is crucial for the effective use of genetic resources to guide plant breeding. Using the whole-genome bisulfite sequencing, we map cytosine methylation at single-base resolution across the whole genome of cotton anthers, and changes in the methylome of the cytoplasmic male sterility system associated with HT stress were analysed in two cotton lines with contrasting HT stress tolerance. The cotton anther genome was found to display approximately 31.6%, 68.7%, 61.8%, and 21.8% methylation across all sequenced C sites and in the CG, CHG, and CHH sequence contexts, respectively. In an integrated global methylome and transcriptome analysis, only promoter-unmethylated genes showed higher expression levels than promoter-methylated genes, whereas gene body methylation presented an obvious positive correlation with gene expression. The methylation profiles of transposable elements in cotton anthers were characterized, and more differentially methylated transposable elements were demethylated under HT stress. HT-induced promoter methylation changes led to the up-regulation of the mitochondrial respiratory chain enzyme-associated genes GhNDUS7, GhCOX6A, GhCX5B2, and GhATPBM, ultimately promoting a series of redox processes to form ATP for normal anther development under HT stress. In vitro application of the common DNA methylation inhibitor 5-azacytidine and accelerator methyl trifluoromethanesulfonate demonstrated that DNA demethylation promoted anther development, while increased methylation only partially inhibited anther development under HT stress.

Rearrangement of N-tert-Butanesulfinyl Enamines for Synthesis of Enantioenriched α-Hydroxy Ketone Derivatives.

Treating chiral N-tert-butanesulfinyl ketimines with potassium hexamethyldisilazide (or potassium tert-butoxide) and methyl triflate gives N-methylated N-tert-butanesulfinyl enamine intermediates that undergo stereoselective [2,3]-rearrangement to afford α-sulfenyloxy ketones with excellent enantiopurities. This cascade of enamination-N-methylation-rearrangement was even used to generate acyclic tertiary α-hydroxy ketones bearing two α-substituents showing negligible differences in bulkiness, such as methyl and ethyl groups.

Evaluation of the Binding Characteristics of [5-11C-methoxy]Donepezil in the Rat Brain for In Vivo Visualization of Acetylcholinesterase

Donepezil, an acetylcholinesterase (AChE) inhibitor, has not been evaluated for its binding characteristics using a radioactive tracer, although its inhibitory action on AChE has been studied. The aim of this research is to examine whether AChE can be visualized in vivo and in vitro with [11C]donepezil. [5-11C-methoxy]Donepezil was synthesized by O-methylation using [11C]methyl triflate. The binding of [11C]donepezil to brain homogenates was higher in the brain stem and striatum, and it was lowest in the cerebellum. The in vitro autoradiographic study successfully demonstrated the specific binding of [11C]donepezil to AChE in the rat brain. The IC50 value of binding was approximately 10 nM, which is comparable to the reported value for inhibiting enzyme activity (6 nM). Saturation experiments revealed that the Bmax and Kd of [11C]donepezil binding in vitro are 65 fmol/mg tissue and 39.8 nM, respectively. In accordance with the in vitro bindings, the in vivo distribution of [11C]donepezil was heterogeneous in the rat brain. In the blocking experiments, the heterogeneous distribution disappeared in the presence of a large amount of unlabeled donepezil. These data suggest that [5-11C-methoxy]donepezil can be potentially useful to image AChE non-invasively in the human brain by positron emission tomography.

Fully-automated radiosynthesis of the amyloid tracer [11C] PiB via direct [11C]CO2 fixation-reduction

BackgroundThe β-amyloid radiotracer [11C] PiB is extensively used for the Positron Emission Tomography (PET) diagnosis of Alzheimer’s Disease and related dementias. For clinical use, [11C] PiB is produced using the 11C-methylation method ([11C] Methyl iodide or [11C] methyl triflate as 11C-methylation agents), which represents the most employed 11C-labelling strategy for the synthesis of 11C-radiopharmaceuticals. Recently, the use of direct [11C]CO2 fixation for the syntheses of 11C-tracers has gained interest in the radiochemical community due to its importance in terms of radiochemical versatility and for permitting the direct employment of the cyclotron-produced precursor [11C]CO2.This paper presents an optimised alternative one-pot methodology of [11C]CO2 fixation-reduction for the rapid synthesis of [11C] PiB using an automated commercial platform and its quality control.Results[11C] PiB was obtained from a (25.9 ± 13.2)% (Average ± Variation Coefficient, n = 3) (end of synthesis, decay corrected) radiochemical yield from trapped [11C]CO2 after 1 min of labelling time using PhSiH3 / TBAF as the fixation-reduction system in Diglyme at 150 °C. The radiochemical purity was higher than 95% in all cases, and the molar activity was (61.4 ± 1.6) GBq/μmol. The radiochemical yield and activity (EOS) of formulated [11C] PiB from cyclotron-produced [11C]CO2 was (14.8 ± 12.1)%, decay corrected) and 9.88 GBq (± 6.0%), respectively. These are higher values compared to that of the 11C-methylation method with [11C]CH3OTf (~ 8.3%).ConclusionsThe viability of the system PhSiH3 / TBAF to efficiently promote the radiosynthesis of [11C] PiB via direct [11C]CO2 fixation-reduction has been demonstrated. [11C] PiB was obtained through a fully automated radiosynthesis with a satisfactory yield, purity and molar activity. According to the results, the one-pot methodology employed could reliably yield sufficiently high tracer amounts for preclinical and clinical use.

Scandium-Promoted Direct Conversion of Dinitrogen into Hydrazine Derivatives via N-C Bond Formation.

Direct conversion of dinitrogen (N2) into organic compounds, not through ammonia (NH3), is of great significance both fundamentally and practically. Here we report a highly efficient scandium-mediated synthetic cycle affording hydrazine derivatives (RMeN-NMeR') directly from N2 and carbon-based electrophiles. The cycle includes three main steps: (i) reduction of a halogen-bridged discandium complex under N2 leading to a (N2)3--bridged discandium complex via a (N2)2- intermediate; (ii) treatment of the (N2)3- complex with methyl triflate (MeOTf), affording a (N2Me2)2--bridged discandium complex; and (iii) further reaction of the (N2Me2)2- complex with the carbon-based electrophile, producing the hydrazine derivative and regenerating the halide precursor. Furthermore, insertion of a CO molecule into one Sc-N bond in the (N2Me2)2--scandium complex was observed. Most notably, this is the first example of rare-earth metal-promoted direct conversion of N2 to organic compounds; the formation of C-N bonds by the reaction of these (N2)3- and (N2Me2)2- complexes with electrophiles represents the first case among all N2-metal complexes reported.

Polymethylation reactions of saturated and unsaturated thiacrown ethers

Saturated thiacrown ether 12S4 (1 mmol) reacted with methyl trifluoromethanesulfonate (1 and 2 mmol) in dichloromethane at room temperature to give mono- and dimethylated products. When the reaction of 12S4 with excess methyl trifluoromethanesulfonate was carried out, a tetramethylated product was obtained as a single isomer. The crystal structures of the mono- and dimethylated products were determined by X-ray crystallographic analysis. Unsaturated thiacrown ether 15UT5 also reacted with methyl trifluoromethanesulfonate to give mono- and dimethylated products.