Abundant Intramolecular Ring Rearrangements of 1-(N-Benzyloxycarbonylamino)arylmethylphosphonate Phenyl monoesters Under Electrospray Ionization Conditions

Abstract

The mass spectrometric behavior of 1-(N-benzyloxycarbonylamino)arylmethyl-phosphonate phenyl monoesters was investigated under positive ion electrospray ionization conditions. All nitrogen-protonated title compounds undergo four- and/or six-membered ring rearrangements to yield nitrogen-containing fragment ions by consecutive or simultaneous loss of a carbon dioxide and phenyl hydrogen phosphonate or phenyl benzylphosphonate or an arylmethylimine. All oxygen-protonated title compounds undergo four- to six-membered ring rearrangements to produce fragment ions by loss of a carbon dioxide plus an arylmethylimine, or phenyl benzylphosphonate, by consecutive or simultaneous loss of benzyl phenyl ether and isocyanic acid. The fragmentation is obviously different from the corresponding methyl and ethyl monoesters, which show a tendency to undergo intramolecular four-membered ring rearrangements only.

GRAPHICAL ABSTRACT      

Stereochemical studies, 73. Saturated heterocycles, 60

N-Substituted-2-carboxamido-1-cycloalkanols were cyclized with 1,1-carbonyldiimidazole to synthesizecis- andtrans-N-alkyl-,N-aralkyl- andN-aryl-2,4-dioxo tri- and tetramethyleneperhydro-1,3-oxazines. The structures of the compounds and theircis ortrans ring anellation were confirmed by IR,¹H- and¹³C-NMR spectroscopy, and thecis andtrans pairs of isomers were compared to establish the predominant conformation of the flexiblecis isomers. It was found that—similarly to the 1,3-oxazin-2- and -4-ones studied earlier—the O-endo conformers are preferred, in which the 1-oxygen atom isaxial to the alicyclic ring; this is independent of the number of ring atoms in the alicycle, and of the presence of an oxazinedione ring, even though this is more flexible that the ring of oxazinones.

---

Synthese und Konformation voncis undtrans 2-substituierten kondensierten 1,3-Oxazin-2,4-dionen

Zusammenfassung cis- undtrans-N-Alkyl-,N-Aralkyl- undN-Aryl-2,4-dioxo-, tri- und tetramethylen-perhydro-1,3-oxazine wurden aus 2-Carboxamido-1-cycloalkanolen und 1,1-Carbonyldiimidazol dargestellt. Mit Hilfe der IR,¹H- und¹³C-NMR Spektroskopie wurden die Struktur, diecis- odertrans-Annellierung der Ringe und die bevorzugte Konformation der flexiblencis-Isomeren im Vergleich zumcis-trans Isomerenpaar nachgewiesen. Ähnlich zu den früher untersuchten 1,3-Oxazine-2- und -4-onen ist hier ebenfalls das O-endo Konformere bevorzugt; in diesem ist der Sauerstoffaxial angeordnet, und zwar unabhängig von der Zahl der alicyklischen Ringatome und dem flexibleren Oxazindionring.

     

Photochemical properties and the structure of 6-methyl-2,4-diphenyl-1-(p-tolyl)pyrimidinium perchlorate and the product of its photocyclization

The structure and photochemical properties of 6-methyl-2,4-diphenyl-1-(p-tolyl)pyrimidinium perchlorate (1) and 4,8-dimethyl-2-phenylpyrimido[1,2-f]phenanthridinium (2) formed as a result of photocyclization of1 have been studied. The crystal structure of compound1 has been studied at –140 °C and 25 °C. In cation1, theN-tolyl substituent and -Ph ring are noncoplanar with the pyrimidinium fragment (the angles are 67.9° and 41.1°, respectively), while the angle between the -Ph ring and the pyrimidinium moiety is only 7.1° (–140 °C). The photocyclization product2 has a flattened structure.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1731–1735, September, 1995.This work was partly (studies performed at Scientific Research Institute of Physical and Organic Chemistry at Rostov State University) supported by the Science Foundation Russian Universities.     

Ab initio Study of the Structure and Vibration Spectrum of N-Methyl-N-(trifluorosilylmethyl)acetamide

The effect of the OSi donor-acceptor interaction on the geometric and electronic structure of N-methyl-N-(trifluorosilylmethyl)acetamide, and also the band frequencies and intensities in the vibration spectrum of this compound were studied by ab initio calculations in the RHF(6-31G*) approximation. The geometry, charge distribution pattern, and energy and nature of molecular orbitals show that the Oarr;Si interaction is mainly determined by interaction of the oxygen lone electron pairs with the * orbitals of the C-Si-F_a fragment. The interaction of the occupied orbitals of the N-C = O fragment with the unoccupied orbitals of the Si(F_e)₂ fragment of suitable symmetry is weaker.     

Unusual dynamics of ring probes in linear matrices

We perform Monte Carlo simulations of ring and linear polymers in linear matrices, and investigate the diffusivity of the probes. As the matrix chain length N_m is increased from 10 to 300 monomers, the diffusivity D_l of a linear probe (N_l = 300) decreases monotonically, while that of a ring probe D_r varies non‐monotonically, with a peak around . We perform additional simulations with a single probe molecule ( ) in a linear matrix ( ). The non‐monotonicity in D_r persists even after ring–ring interactions are eliminated. Topology dependent differences in the short‐time dynamics of the probes are observed; unlike linear probes, mean‐squared displacements of ring probes depend on N_m. Primitive path analysis suggests that the difference in dynamics originates from differences in entanglement structure. For linear probes, the degree of entanglement is independent of N_m. For ring probes, we observe two regimes: when N_m is small, the number of threadings decreases as N_m increases, eventually transitioning to a plateau. In the small N_m regime, the change in the degree of entanglement offsets the change in the mobility of the matrix chains, leading to a non‐monotonic variation in D_r. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 169–177     

Specific Features of Reactions of Halomethyl Derivatives of Alkyl 5-Isobutylfuran-3-carboxylates with Trimethyl Phosphite and Sodium Diethyl Phosphite

Ethyl 5-isobutyl-2-methylfuran-3-carboxylate is selectively brominated with N-bromosuccin-imide by the methyl group to give an unstable bromide. The latter on heating or in the presence of bases un-dergoes dehydrobromination accompanied by rearrangement, leading to a (2'2-dimethylvinyl)furan derivative.Phosphorylation of this bromide with trimethyl phosphite gives a 2-dimethoxyphosphorylmethyl derivativeand a product containing the phosphonate group to the isobutyl radical. Chloromethylation of the startingester proceeds in the 4 position of the furan ring. The resulting chloride undergoes phosphorylation underconditions of the Michaelis-Becker reaction to give the corresponding 4-(dialkoxyphosphorylmethyl)furan'and under the action of trimethyl phosphite a mixture of the same phosphonate, a dehalogenation producthaving a dimethylvinyl fragment. Bromination of the 4-chloromethyl derivative with N-bromosuccinimideinvolves the 2-methyl group. The dihalide reacts with trimethyl phosphite by way of reduction of the bromomethyl group to give 4-chloromethyl- or 4-dimethoxyphosphorylmethyl derivatives, as well as analogous dehydrohalogenation products containing a 5-dimethylvinyl fragment. A scheme describing the sequence of formation of these products in the course of the reaction is offered.     

Structure and Tautomerism of Cyclopentadiene Derivatives: IX. Synthesis and Structure of Substituted N-Cyclopentadienyl Amidinium Ylides

A procedure has been developed for the synthesis of N-cyclopentadienyl amidinium ylides of the general formula C₅(CO₂Me)₄[ArNC(Ar')NHAr]. According to the X-ray diffraction data, ¹H and ¹³C NMR spectroscopy, and MNDO quantum-chemical calculations, the title compounds have a zwitterionic structure with the positive charge localized over the amidine NÄCÄN triad, and the negative charge, over the cyclopentadiene fragment. The configuration of the amidine moiety is stabilized by additional interaction of the NH hydrogen atom with the negatively charged cyclopentadiene ring (-bonding). The ylides are chiral due to atropoisomerism arising from a high energy barrier (G 298 >25 kcal/mol) to rotation of the Ar' substituent about the ordinary CÄC bond in the amidinium fragment.     

Coupling of o and/or m-substituted arylamines with the ortho-C–H function of the pendant aryl ring in coordinated arylazopyrimidinepalladium(II) complexes. Spectral and electrochemical characterisation of the products

2-(Arylazo)pyrimidines (aapm) are N,N-chelators which form palladium(II) complexes, Pd(aapm)Cl₂ (1). The reaction of Pd(aapm)Cl₂ (1) with arylamines (ArNH₂) yields Pd(aapm-N-Ar)Cl, (2)–(7), complexes of the tridentate N,N,N-donor system in which arylamines are fused to the ortho C–H function of the pendant aryl ring in the coordinated 2-(arylazo)pyrimidine, leading to the C–N coupled product. Pd(aapm-N-Ar)Cl, complexes (2)–(7), exhibit a broad intense absorption band in n.i.r. region (870–920 nm), while the parent complex, Pd(aapm)Cl₂, shows an intense absorption at 425 nm. Cyclic voltammograms of (2)–(7) exhibit an oxidation couple at positive potential to s.c.e. together with three reductions at negative side. The oxidation may involve conversion of the chelated azoarylamine to semibenzoquinone azoarylamine fragment. The reduction is due to the accommodation of electrons in the azoimine function. The absorption spectra in the n.i.r. region may be regarded as HOMO LUMO intravalence charge transfer (i.v.c.t.) transitions.     

Structural study of alternating copolymerization of aziridines with cyclic imide

The structures of copolymers of aziridines with cyclic imides were determined by means of infrared spectrometry, paper electrophoresis of the hydrolyzate, and NMR spectrometry. The structure of the repeating unit in the copolymer of ethylenimine with succinimide was \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--} ({\rm CH}_2 {\rm CH}_2 {\rm NHCOCH}_2 {\rm CH}_2 {\rm CONH}\rlap{--} ) $\end{document}. The endgroups of the copolymer were N-acylethylenimine ring, N-substituted succinimide ring, and primary amide group. The copolymer of ethylenimine with N-ethylsuccinimide had the repeating unit of \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm CH}_2 {\rm CH}_2 {\rm NHCOCH}_2 {\rm CH}_2 {\rm CON}({\rm C}_2 {\rm H}_5 )\rlap{--} ] $\end{document} and the endgroups of N-acylethylenimine and N-substituted succinimide ring. N-Ethylethylenimine did not copolymerize with succinimide, but in the presence of water, the reaction occurred to give an amorphous polymer. This copolymer had the repeating unit \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm CH}_2 {\rm CH}_2 {\rm NHCOCH}_2 {\rm CH}_2 {\rm CON}({\rm C}_2 {\rm H}_5 )\rlap{--} ] $\end{document} and the endgroups were N-substituted succinimide ring and amine group but not N-acylethylenimine ring. On the basis of this structural information, the initiation reaction was discussed.     

Lithiation of N‐protected‐dihydro‐1,4‐benzoxaziness

Lithiation of N‐protected‐2,3‐dihydro‐1,4‐benzoxazines is described. Lithiation of N‐(tert‐butoxycarbonyl)‐2,3‐dihydro‐1,4‐benzoxazine ( 1 ) with BuLi/TMEDA occurred in the α‐position to nitrogen on the heterocyclic ring, leading to the unexpected ring‐opened product 3 . On the other hand, lithiation of N‐methyl‐2,3‐dihydro‐1,4‐benzoxazine ( 4 ) took place at the oxygen‐adjacent ortho‐position of the aromatic ring.     

Design, synthesis, and structural aspects of chalcogen-substituted pyridine dicarboxamide donors and their reactions

The design and synthesis of a new family of potentially pentadentate N₃Se₂ or N₃Te₂ type donors bearing a 2,6-disubstituted pyridine dicarboxamide moiety as the central fragment [-NH-C(O)-pyridine-C(O)-NH-] functionalized with chalcogen as additional donors in the appended arms of the pyridine ring through the alkyl spacers and their potential applications and reactivity toward d⁸ and d¹⁰ metal ions have been demonstrated.     

Steric effect of terminal substituents in azomethins and thermal stability of the nematic phase

The paper studies the steric eflect of terminal substituents on the temperature T_c of the phase transition nematic liquid crystal-isotropic liquid in mesogenic azomethins with one or two noninteracting or strongly interacting conformation degrees of freedom. The linear dependence T_c(Q) has been confirmed, where Q=(cos² _N) is the conformation paramefer of the molecular ensemble; _N is the angle between the planes of the bridging group CH=N and the aniline ring in the benzylideneaniline fragment. Direct and indirect steric eflects of lateral substituents are shown to take place, which explain an anomalous variation of T_c in some compounds upon substitutions in them.L. V. Kirensky Institute of Physics, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 4, pp. 89–97, July–August, 1993.Translated by L. Smolina     

Structural characterization of the trans-equatorial isomer of (aqua)(ethylenediamine-N,N,N′-tripropionato)chromium(III) trihydrate,[Cr(edtrp)(H2O)] · 3H2O

The structure of trans-equatorial [Cr(edtrp)(H₂O)] · 3H₂O (edtrp^3– is the anion of ethylenediamine-N,N,N-tripropionic acid) was determined by single crystal X-ray diffraction. The chromium(III) ion is surrounded octahedrally by the two nitrogen and three oxygen atoms of the quinquedentate edtrp^3–, forming a five-membered diamine ring and the three six-membered -propionato chelate rings. The remaining coordination position is occupied by the H₂O ligand. The crystal structure conformation is compared to the result of recent molecular mechanics analysis. The ring strain of R and G chelate rings was found to be in agreement with the previously proposed mechanisms for the C—N bond cleavage and recombination.     

Crystal structures of phenyl-substituted cyclopropanes. IV. the crystal structure (at 21‡C and −100‡C) and the phenyl ring conformation in 4-cyclopropylacetanilide

The crystal structure of 4-cyclopropylacetanilide was investigated at room temperature (21C) and at –100C in order to determine the orientation of the phenyl ring with respect to the cyclopropane moiety and the effect of this substituent on the stereochemistry of the three-membered ring. The compound was chosen because it is one of the few species containing a simple phenyl ring as the sole cyclopropane ring substituent and whose crystals are suitable for X-ray diffraction at room temperature. The substance crystallizes in space groupP2_l/c at either temperature (no phase transitions) with cell constants: (at 21C)a=9.725(2),b=10.934(3), andc=9.636(2) å,=106.13(1);V=984.21 å³ andd(calc;z=4)=1.182 g cm^–3. The relevant parameters for the –100C structure area=9.557(4),b=10.980(2), andc=9.641(2) å,=106.34(3);V=970.76 å³ and d(calc;z=4)=1.199 g cm^–3. Final values wereR(F)=0.042, R_w=0.035, using unit weights, and its nonhydrogen atoms were used to phase the low-temperature data, whose final discrepancy indices wereR(F)=0.051,R _w =0.061. The phenyl substituent is almost exactly in the bisecting conformation with respect to the C-C-C angle at the point of attachment to cyclopropane and conjugative effects are clearly evident in the lengths of the cyclopropane ring [1.494(3), 1.498(3), and 1.474(4) å, the later being the distal bond]. If one omits the terminal methylene fragments at C10 and C11, the atoms comprising the acetanilide fragment and the substituted carbon of the cyclopropane ring lie in a nearly perfect plane. Molecular mechanics as well as semiempirical (AM1) calculations were carried out in order to determine the structure of the energy-minimized configurations in the two computational environments. The molecular conformations thus obtained are close to that experimentally observed from the X-ray diffraction experiment. In both theoretical models, the lowest energy conformation is that in which the plane of the phenyl ring bisects the cyclopropane C-C-C angle as was experimentally observed. Finally, the shape of the conformational barrier as a function of the orientation of the plane of the phenyl ring was computed, giving a maximum barrier to rotation of 2.2 kcal/mol. Similar calculations were carried out for two other aryl cyclopropanes, whose rings (naphthalene and anthracene) cannot adopt the bisecting position. Comparisons of experimental geometrical parameters as well as of the barriers to rotation are presented.on leave at the University of Houston, 1995–1996.     

Direct metalation of poly(2,6-dimethyl-1,4-phenylene ether)

Poly(2,6-dimethyl-1,4-phenylene ether) (I) was metalated with butyllithium in tetrahydrofuran and with the N,N,N′,N′-tetramethylethylenediamine complex of butyllithium in a variety of solvents. In these cases, metalation occurred at both the ring and side chain positions, the former being preferred initially. Subsequently, there was an isomerization in favor of the side chain. At 25°C, there is no significant amount of polymer scission or crosslinking during metalation, but some crosslinking occurs on derivatizing with dimethyl sulfate and trimethylchlorosilane for high extents of ring metalation. With sodium and potassium alkyls, only side-chain metalation was observed. The metalated polymer reacts as a typical organometallic, allowing polymer modification by a wide variety of reactions.     

Synthesis, structure and thermal analysis of the gallium complex of 1,4,7,10-tetraazacyclo-dodecane-N,N′,N″,N-tetraacetic acid (DOTA)

As part of our efforts to synthesize gallium bioconjugates based on folic acid and thiamin we have utilized 1,4,7,10-tetraazacyclo-dodecane-N,N′,N″,N-tetraacetic acid (DOTA) as the chelating ligand for gallium(III). The reaction of gallium chloride with DOTA at room temperature in aqueous solution affords the complex [Ga(HDOTA) · 5.5H₂O] (1), which is characterized by single-crystal X-ray spectroscopy, electrospray mass spectrometry and thermal gravimetric analysis. Gallium displays 6-coordinate distorted octahedral geometry within a puckered macrocyclic DOTA framework. The equatorial plane comprises two nitrogens of the DOTA ring and two oxygens from two of the four pendant carboxylic acid groups. The axial positions are comprised of the remaining two transannular nitrogens of the DOTA ring.     

Distortion of Configuration of the Nitrogen Atom in 3-Trimethylsilylpropynamides

Analysis of the IR spectral parameters and the results of AM1 quantum-chemical calculations indicated distortion of the planar structure of the amide fragment and destabilization of the nitrogen configuration in new N-functionalized 3-trimethylsilylpropynamides Me₃SiCCC(O)NHR. This effect is most pronounced in N-hydroxy-3-trimethylsilylpropynamide upon formation of intramolecular hydrogen bond C=O···H-O.     

Electrochemical reduction and oxidation of fullerenopyrrolidines and the ESR spectra of paramagnetic intermediates

Electroreduction and electrooxidation of monosubstituted N-methyl[60]fullerenopyrrolidines were studied by cyclic voltammetry and potentiostatic microelectrolysis in the cavity of an ESR spectrometer. Stepwise reversible transfer of three electrons to the fullerenopyrrolidine molecule results in the formation of stable radical anions (according to ESR, g = 2.0000, H = 0.8 G), dianions, and radical trianions (according to ESR, g = 2.0015, H = 1.5 G). The reduction potentials vary over narrow limits depending on the nature of the substituents in the pyrrolidine fragment of the compounds. Electrooxidation is irreversible and occurs in either one or two steps. For compounds containing the aniline, indole, or phenol fragment, the first step is associated with oxidation of these fragments and only after that, is the fullerenopyrrolidine core oxidized. Oxidation of the pyrrolidine fragment is substantially more difficult than that of tertiary amines.     

Chiral photochromic 2-(N-acyl-N-arylaminomethylene)benzo[b]thiophen-3(2H)-ones

Photochromic 2-(N-acyl-N-arylaminomethylene)benzo[b]thiophen-3(2H)-ones containing ortho-substituents in the N-phenyl ring were studied by X-ray diffraction analysis and ¹H NMR spectroscopy. It was established that these compounds have stable chiral structures due to hindered rotation of the phenyl ring around the C—N bond. The energy barrier to racemization evaluated by dynamic NMR spectroscopy is G ^# _{428 K} = 98 kJ mol^–1.     

Some structural problems and the vibration spectra of a series of N-substituted ethylenimines

On a basis of comparison of Raman and IR absorption spectra, as well as measurements of intensities and degrees of depolarization of Raman lines, pulsation (breathing) vibrations of the ethylenimine ring - _sNin a series of N-substituted ethylenimines are identified. Alkyl substituents increase _sNas compared with ethylenimine, probably because of change in the hydridization of the electron clouds of the nitrogen due to steric causes. The high values of _sNfor substituents capable of conjugation effects, is in accord with the hypothesis that the lone electron pair of the nitrogen participates in conjugation. Furthermore, when N enters into the composition of a 3-membered ring, the lone pair exhibits diminished capacity for delocalization. The intensity of the Raman line _sN of N-phenylethylenimine is anomalously high, and the cause of this requires explaining. UV spectra are given.