Fluorocarbon derivatives of nitrogen. Part 11. Synthesis of some 2-(trifluoromethyl)imidazo[1,2-a]pyridines from trifluoroacetonitrile

3-(t-Butoxycarbonyl)-2-(trifluoromethyl)imidazo[1,2-$\text{a}$]-pyridine, prepared from trifluoroacetonitrile and pyridinium t-butoxycarbonylmethylide, reacts smoothly with trifluoroacetic acid to provide 2-(trifluoromethyl)imidazo[1,2-$\text{a}$]pyridine-3-carboxylic acid, which gives 2-(trifluoromethyl)imidazo[1,2-$\text{a}$]-pyridine when heated. 3-Cyano-2-(trifluoromethyl)imidazo[1,2-$\text{a}$]pyridine can be obtained $\text{via}$ treatment of trifluoroacetonitrile with pyridinium cyanomethylide, which is sufficiently reactive to effect nucleophilic displacement of fluorine from pentafluoropyridine under mild conditions [→pyridinium cyano(tetrafluoro-4-pyridyl)methylide].     

Nucleophilic substitution by arenethiolates at the carbene carbon of pentacarbonyl(methoxymethylcarbene)-metal(o) complexes (metal = Cr,Mo, or W)

The phenylthiocarbene complexes, [(CO)₅MC(CH₃)(SPh)] (M = Cr, Mo, or W) have been prepared in good yield by the reaction of [(CO)₅MC(CH₃)(OCH₃)] (M = Cr, Mo, or W) with NaSPh in benzene/methanol in the presence of HCl. A series of para-substituted phenylthiocarbene complexes of tungsten. [(CO)₅WC(CH₃)SC₆H₄Y)], (Y = p-Br, p-F, p-H, p-CH₃, p-OCH₃ or p-OH) have also been prepared by the reaction of the appropriate arenethiolate ion with [(CO)₅WC(CH₃)(OCH₃)]. Poor nucleophiles such as p-nitrobenzenethiolate and pentafluorobenzenethiolate did not react with [(CO)₅WC(CH₃)(OCH₃) to form the corresponding phenylthiocarbene complex. A mechanism accounting for the formation of these phenylthiocarbene complexes is proposed. The complexes have been characterized by their infrared, electronic, mass, ¹H NMR, and ¹³C NMR spectra. These spectroscopic data have been used to establish the structure of these complexes in solution and indicate that the phenyl ring bonded to sulfur is probably not coplanar with the “carbene” plane.     

Gas-phase electron diffraction determination of the molecular structure of perfluoro(methyloxirane)

The molecular geometry of perfluoro(methyloxirane) has been studied using gas-phase electron diffraction data, effective least-squares refinement of the structure being achieved with the aid of constraints to limit the number of variable parameters. With the CCF₃ bond constrained to be 0.078 Å longer than the ring CC, the refined bond- length values CF (av.) = 1.323(2), CO (av.) = 1.410(8), and CC (ring) = 1.467(7) Å ($\text{r}$_g values, with e.s.d. in parentheses) were obtained; the angles between ring bonds and substituent CF bonds were CCF (av.) 121(1) and OCF (av.) 114(1)^o, the corresponding parameters involving the bulkier CCF₃ fragment being larger by 3^o in each case [∠CCCF₃ 124(1)^o∠OCCF₃ 117(2)^o]. The remaining refined parameters were ∠CCF(of CF₃) = 110.6(4)^o and τ , a torsion angle defining the orientation of the CF bonds of the CF₃ group with respect to ring bonds, = 29(2)^o. Dependent bond angles possessed the values 62.7 (COC), 58.7 [OCC (ring)], 108.3 [FCF (CF₃ group)], 114 [FCF (ring CF₂)], and 111^o (FCCF₃).     

A comparative study of polyurethane-poly(methyl methacrylate) interpenetrating and semi-1 interpenetrating polymer networks

Polyurethane(PUR)-poly(methyl methacrylate) (PAc) semi-1 interpenetrating polymer networks of various compositions have been prepared. They show several differences from the corresponding full IPN's. Thus, the rate of polymerization of the acrylic phase is lower. Transparent plates are also more difficult to obtain. Both effects are ascribed to the absence of the crosslinking agent of the second phase. The composition also plays a role in transparency. Solvent extraction shows that, with increasing PUR content, more PAc remains entrapped in the PUR network. The transition behaviour indicates that the phases are less entangled in semi-IPN's than in IPN's. Consequently, the effect of crosslinking or not crosslinking the second component is very important with regard to the properties of PUR/PAc combinations.     

Preparation and studies of a new ammonium vanadium bronze, (NH4)xV2O5

A new bronze-type phase of composition (NH₄)_0.40±0.02V₂O₅ is obtained around 230°C during the thermal decomposition of NH₄VO₃ in hydrogen atmosphere. The bronze intermediate is characterized by X-ray diffraction, electrical conductivity, magnetic susceptibility, and ESR studies. It is found to be isostructural with other known β-type vanadium bronzes of general formula M_xV₂O₅, where M is usually a monovalent metal. Electrical conductivity and magnetic studies indicate the localized character of conduction electrons at V⁺⁴ sites. At high temperatures (>400°C), the bronze undergoes decomposition and subsequent reduction to V₂O₃ in hydrogen atmosphere.     

N-halogeno-compounds. Part 9 [1]. Azoxy- and azo-arenes derived from 4-(dichloroamino)tetrafluoropyridine; crystal structure of trans-2,3,5,6-tetrafluoro-4-(2,4,6-trimethylphenyl-onn-azoxy)pyridine

The nitrosoarenes ArNO (Ar = C₆H₅, 2-MeC₆H₄, 2,4,6- Me₃C₆H₂ and C₆F₅) have been condensed with 4-(dichloroamino)- tetrafluoropyridine to provide the azoxy-compounds py_FN$\text{N}\text{+}$($\text{N}\text{-}$)Ar (py_F = 2,3,5,6-tetrafluoro-4-pyridyl); de-oxygenation of the first three with triphenylphosphine or triethyl phosphite gave the corresponding azo-compounds, and the reverse reaction was achieved in the case of py_FNNC₆H₂Me₃-2,4,6 using peroxytrifluoroacetic acid. Thermolysis of 4-azidotetrafluoropyridine in the presence of pentafluoronitrosobenzene provided the perfluorinated azoxy-compound py_FN$\text{N}\text{+}$($\text{O}\text{-}$)C₆F₅. X-Ray methods have been used to determine the molecular geometry of py_FN$\text{N}\text{+}$($\text{O}\text{-}$)C₆H₂Me₃-2,4,6.     

Preparation,stability, reactivity and synthetic utility of a cadmium stabilized complex of difluoromethylene phosphonic acid ester

Diethyl bromodifluoromethyl phosphonate reacts readily with cadmium metal to form a stable cadmium complex. Depending on solvent, this functionalized organocadmium reagent exhibits stability for days to months. It reacts with a variety of electrophiles and serves as a synthetically useful source for the introduction of the difluoromethylene phosphonate group into organic compounds.The synthetic utility of a wide variety of fluoromethylene phosphonium ylides has been a major effort in our laboratory over the past several years [1]. The generation and capture of difluoromethylene ylides ($\text{1}$) as a general route to difluoromethylene olefins has been of especial interest to us [2]. In an effort to increase the nucleophilicity of the ylide, we have attempted to prepare the analogous phosphonate ylide ($\text{2}$). Although we have achieved modest success [3] by $\text{insitu}$ capture of ($\text{2}$) in the reaction of

sodium dialkyl phosphites with diethyl bromodifluoromethylphosphonate ($\text{3}$), attempts to pregenerate ($\text{2}$), either from diethyl difluoromethylphosphonate ($\text{4}$) or ($\text{3}$), have met with little success. ($\text{2}$) appears to have minimal stability even at low temperatures, and scale up processes of synthetic value would seem to be difficult.     

Fluorocarbon derivatives of nitrogen. Part 10. Preparation of heptafluoro- and 1-chlorohexafluoro-2-nitrosopropane,and conversion on the latter to chloropentafluoroacetone oxime

Details are given for the preparation of heptafluoro-2-nitrosopropane and 1-chlorohexafluoro-2-nitrosopropane $\text{via}$ the routes CF₃CFCF₂ → [with CsFR_FCO₂Ag (R_F = CF₃, nC₃F₇)] (CF₃)₂CFAg → (with NOCl) (CF₃)₂CFNO and CF₃CFCF₂ → (with CsClNOCl) CF₃(CF₂Cl)CFNO, respectively, and for conversion of the latter nitroso-compound to chloropentafluoroacetone oxime $\text{via}$ reduction with aqueous potassium hydrogen sulphite.     

Nitroxide chemistry. Part XIX. Reaction of bistrifluoromethyl nitroxide with diphenylketene and related compounds (Ph2CHCOX,X  OH,Cl, NH2)

The following reactions have been accomplished: 2(CF₃)₂NO· + Ph₂CCO → Ph₂C[ON(CF₃)₂]CO₂N(CF₃)₂ → (on hydrolysis) Ph₂C[ON(CF₃)₂]CO₂H; 2 (CF₃)₂NO· + Ph₂CHCOX → (CF₃)₂NOH + Ph₂C[ON(CF₃)₂]COX (X  OH, Cl,NH₂).     

A novel synthesis of 3-fluorophenylalanine and some of its derivatives

Ring opening of 2-cyano-3-phenylaziridine and 2-amido-3-phénylaziridine by HF/pyridine was found to give 2-amino-3-fluorophenylpropionitrile (IV) and 2-amino-3-fluorophenylalanamide (VII) respectively. 3-fluorophenylalanine (V) could be obtained by an acidic hydrolysis of (IV) or (VII) whereas isopropyl-3 fluorophenylalanate (VI) was isolated by esterification of (V) or by heating (IV) with iso-propanal-12 NHCl under reflux.     

Some reactions of grignard reagents with chloroform and carbon tetrachloride in the presence of cyclohexene

The reactions of phenylmagnesium bromide and ethylmagnesium iodide with carbon tetrachloride in the presence of cyclohexane are reported. The identified products include 3,3′- bicyclohexenyl, dichloromethylcyclohexane, 7,7-dichloronorcarane, 7,7-dibromonorcarane and 7-bromo-7-chloronorcarane. The phenyl Grignard reagent reacts primarily by an ionic pathway, whilst a radical mechanism also occurs with the ethyl Grignard reagent.     

The kinetics of the polymerization of methyl methacrylate initiated by t-butylmagnesium bromide in THF,toluene or mixed solvent

The kinetics of the solution polymerization of methyl methacrylate in THF, toluene and their mixtures were studied between 200 and 300 K using dilatometry (in the systems where it was valid), gravimetric determination and monitoring monomer and polymer concentrations by NMR spectrometry. The reaction followed zero order kinetics at 200 K, first order kinetics at 275 K and mixed order in between. At both the limits and intermediate range, the reaction followed an integrated rate equation consistent with terminationless propagation proceeding through a complex between monomer and the propagating species. Above 275 K, termination and side reactions were evident and the yields of high mol. wt polymer were small. Density-temperature calibrations for monomer in THF, toluene and mixtures were constructed for the range 190–283 K. However for polymerizations in toluene-rich mixtures, where very high mol. wt polymer forms, the contraction did not correlate linearly with conversion.     

Synthesis of the stereoisomers of the methylesters of 3-isopropyl-5-methoxy-6-ketoheptanoic acid and of 2-methoxy-4-isopropylhexandioic acid

The four stereoisomers of 3-isopropyl-5-methoxy-6-ketoheptanoic acid methylester and those of 2-methoxy-4-isopropylhexandioic acid methylester were synthesized from R(?)- and S(+)-carvone. The combined data given provide a basis for specific enantiomer assignment to natural product degradation materials.     

Diazotisation of 4-aminotetrafluoropyridine in a sulphuric acid-acetic acid-propionic acid medium

4-Aminotetrafluoropyridine can be diazotised successfully by adding it to a solution of sodium nitrite in a mixture of 98% sulphuric acid, acetic acid and propionic acid; addition of mesitylene, $\text{m}$-cresol, 3, 5-dimethylphenol or 2-naphthol to the solution of tetrafluoro-4-pyridyldiazonium ion thus produced provides the expected azo-compounds in good yields.