Elimination Of HCN Research Articles

Michael Addition and Alkylation of 2-Azaallyl Anions Derived from N-(1-Cyanoalkyl)imines, and Stereoselective Cyclization of Imine Esters or Ketones Leading to 1-Pyrrolines

Abstract The 2-azaallyl anions derived from N-(1-cyanoalkyl)imines and DBU undergo Michael addition or alkylation to produce N-(1-alkylated 1-cyanoalkyl)imines. The Michael addition of some aryl-substituted imines are highly diastereoselective. The alkylated Michael adducts are converted into lactams through a hydrolysis and recyclization sequence. Base-induced cyclization furnishes 1-pyrrolines through a cyclization and HCN elimination sequence. In the latter reaction, 4,5-cis-1-pyrrolines are selectively produced when the adducts are treated with LDA in the presence of lithium iodide.

Stereoselectivity of Cydoaddition of N-(Cyanomethyl)- and N-(α-Cyanobenzyl)imines with Olefinic Dipolarophiles. Synthetic Equivalents of Nitrile Ylide 1,3-Dipoles

Abstract N-(Cyanomethyl)- and N-(α-cyanobenzyl)imines derived from a variety of aldehydes and ketones can tautomerize into N-protonated azomethine ylides which undergo cycloadditions with olefinic dipolarophiles. These cycloadditions are often accompanied by the elimination of HCN, mostly in a stereospecific manner, showing these imines to be synthetic equivalents of nonstabilized nitrile ylides. Stereoselectivity of the cycloadditions is discussed.

A formal total synthesis of aklavinone via a blocked anthraquinone tautomer

An advanced intermediate in the Kishi synthesis of aklavinone was prepared. Juglone was converted into enone 4. Quinone 6 was then prepared from 4 by Michael addition and elimination of PhSOH and HCN.

Identification of two separate mechanisms for HCN loss from gas phase quinoline cations

AbstractCritical energy measurements on 13C‐labelled quinolines show that the energy requirement for elimination of H(C‐2)N from metastable ions is lower than that for H(C‐3)N elimination, the critical energies being 4.03 ± 0.05 eV and 4.17 ± 0.05 eV, respectively. It is also shown that involvement of C‐2 and C‐3 in unimolecular HCN elimination from ions in the second field‐free region is greater, by factors of approximately 3 and 2 respectively, than would be anticipated for elimination following complete carbon randomization.

Synthesis of nitrogen heterocycles by condensation of the conjugate base of open‐chain reissert compound analogs with vinyltriphenylphosphonium bromide (schweizer's salt)

AbstractReaction of the conjugate base of several open‐chain Reissert compound analogs with vinyltriphenylphosphonium bromide is shown to afford a convenient route to substituted pyrroles. The condensation is a two‐step process involving an initial reversible addition to form an unstabilized Wittig reagent followed by an intramolecular Wittig reaction upon the carbonyl group of the tertiary amide functionality with concomitant elimination of HCN. Several applications to the synthesis of 1,2,5‐trisubstituted pyrroles are presented, together with attempts to expand this methodology to the synthesis of other heterocyclic systems.

Temperature dependence of processes during initial stages of oxidation of poly(acrylonitrile‐co‐acrylic acid) films

AbstractPoly(acrylonitrile‐co‐acrylic acid) films containing 1.8 percent acrylic acid as comonomer units in the copolymer were oxidized in air isothermally at different temperatures for periods of 1 and 5 hours. The physico‐chemical properties such as thermogravimetry, differential scanning calorimetry, infrared spectral absorption and intrinsic viscosity were analysed for the oxidized films. The intrinsic viscosity shows that the molecules of the polymer crosslink at temperature as low as 100°C. TGA spectrum shows two regions of steep weight losses in the range of temperatures studied, one is at 275–300°C and the other at 395–485°C. The first region is the formation of ladder polymer with the elimination of NH3, HCN and CO. The second region is due to the formation of aromatic structures with the elimination of HCN, NH3, water vapour and higher hydrocarbons. DSC spectral analysis shows an endothermic effect up to 205°C and exothermic processes from 205–300°C with a peak at 276°C. The exothermic processes continue up to 360°C. The exothermic effect is reduced for the films oxidized at 242 and 275°C. A marked endothermic effect is noticed at 120°C for the films oxidized at 242 and 275°C. This shows that the cyclization accompanying with exothermic effect sufficiently advanced during isothermal treatment leaving less room for rapid cyclization occurring upon further heating. IR spectral data show the negative environment with a shoulder at 2210 cm−1 which is associated with uptake of oxygen during oxidation. Distinct peaks at 810 and 1550–1700 cm−1 are noticed for the oxidized films oxidized at 275°C which are due to the presence of conjugated double bonds of the type C  NC  N. This type of conjugation is assumed in the ladder polymer.

Kinetic Energy Release and Energy Partitioning During the Ionic Fragmentation in Metastable Ions

The kinetic energy released in the unimolecular decomposition of some metastable transitions has been investigated. It was found to have a significant temperature dependence in cases of H‘ loss from molecular ions. This is attributed to the tunelling of H• atom through the centrifugal barrier. The activation energies of the reverse reactions “εr ≠” and the kinetic energy released “TB” have been determined for the loss of H• from acetonitrile and elimination of HCN from benzonitrile. The partitioning energy quotients q=TB/εr ≠ are found = 0.91 and 0.58 for acetonitrile and benzonitrile respectively.

An electron impact study of HCN elimination from indolizine by use of 13C labelling

AbstractThe study of the loss of HCN from the molecular ions of [1‐13C]‐, [2‐13C]‐ and [3‐13C]‐indolizine shows that, if the C‐3 atom is eliminated predominantly, as may be expected, the C‐2 atom, and (a) carbon atom(s) of the hexagonal ring are also involved. The losses of 13CCH3. and C2H3. from the [MH12CN]+˙ ions of the three compounds point to the interference of distinct mechanisms of HCN elimination, leading to different structures for the [C7H6]+˙ ions.

Unexpected structural integrity of gas phase isoquinoline cations that eliminate HCN

Abstract13C labelling has been used to study isoquinoline molecular ions undergoing breakdown by HCN elimination in a mass spectrometer. For otherwise stable ions caused to fragment by collisional activation, there is no skeletal rearrangement prior to HCN loss. Of the ions formed by 70 eV electron impact, 69% of those which fragment in the ion source by HCN loss retain their structural integrity, as do 44% of the metastable ions. Of the ions that eliminate HCN without prior arrangement, approximately two‐thirds eliminate C‐1 and one‐third eliminate C‐3. Critical energies are reported for the elimination of HCN from pyridine and isoquinoline molecular ions.

The course of cyclic ethylene acetal formation from 7a-methyl-2,3,7,7a-tetrahydro-1 H-indene-l,5(6H)-dione

All attempts to convert the dione (1a) [7a-methyl-2,3,7,7a-tetrahydro-1H-indene-1,5(6H)-dione] into the 5-monoacetal (8) [5,5-ethylenedioxy-7a-methyl-4,5,6,7-tetrahydro-2H-inden-l(7aH)-one] by direct ethylene acetal formation under mild conditions have led to complex mixtures usually containing the required monoacetal (8),its conjugated enone isomer (9), the diacetal (5) and the 1-monoacetal (2). The diacetal (5) readily forms a dimer (4) in the presence of anhydrous acid, but in dioxan containing aqueous sulfuric acid it is hydrolysed to the 5-monoacetal (S), isolated in 68% yield after chromatographic separation from the dione (la). For preparative purposes the most convenient and reliable method for the preparation of (8) is conversion of (la) into the 1-cyanohydrin (34), formation of the corresponding 5-acetal (36), and elimination of HCN from the 1-cyanohydrin group with pyridine; this gave the 5-monoacetal(8) in 66% overall yield.

α-Substituierte phosphonate—38: 1-dimethylamino-1-cyano-methanphosphonsäurediethylester, ein neues edukt zur darstellung von carbonsäuren, 1-cyanoenaminen und homoenolaten

Alkylation of 1-dimethylamino-1-cyanomethanephosphonic acid diethyl ester ( 8), easily obtainable from diethyl phosphite and the 0,N-acetal 9, yields 1-alkyl derivatives 14. Elimination of HCN converts 14 into 1-phosphonoenamines 6. Carbonyl compounds react with 8 to give 1-cyanoenamines 15 which may be hydrolyzed to from the homologous carboxylic acid. Alternatively, deprotonation of 15 yields the homoenolate anions 17 which can be alkylated or hydroxyalkylated, permitting chain extension of carbonyl compounds through introduction of an α-carboxyl and a β-alkyl group. Acid catalyzed hydrolysis of 8 results in cleavage of the PC bond, leading to the corresponding α-dimethylamino alkanoic acids. A phosphonic acid 11 can be obtained from 8 by application of the silylester method. An unambigous assignment of E/ Z-isomers of the cyanoenamines 15 has been derived from 13C-NMR spectroscopy.

ChemInform Abstract: KINETICS AND MECHANISM OF THE THERMAL DECOMPOSITION OF CYCLOPENTYL CYANIDE

The thermal decomposition of cyclopentyl cyanide has been investigated in the temperature range of 905–1143 K using both conventional stirred-flow reactor and very low-pressure pyrolysis (VLPP) techniques. The results from both techniques are consistent. The main primary processes are HCN elimination to form cyclopentene: and ring fragmentation to form vinyl cyanide plus propylene and ethylene plus cyanopropenes: Under the experimental conditions cyclopentene undergoes further decomposition to cyclopentadiene plus hydrogen. There is evidence for conversion of some of the reactant to a solid residue, presumably polymer. From the stirred-flow reactor results the following Arrhenius expressions were obtained: log k1(s−1) = (12.8 ± 0.3) − (65.6 ± 1.3)/θ and log k2(s−1) = (16.0 ± 0.3) − (80.0 ± 1.1)/θ, where θ = 2.303RT kcal/mol. Application of RRKM theory shows that the VLPP experimental rate constants are consistent with high-pressure Arrhenius parameters given by log k1(s−1) = (12.8 ± 0.3) − (67.8 ± 2.5)/θ for HCN elimination, and log k4(s−1) = (16.3 ± 0.3) − (80.1 ± 2.0)/θ for the sum of the ring fragmentation pathways. The rate parameters for HCN elimination are in good agreement with previous VLPP studies of alkyl cyanides and with theoretical predictions. The difference in activation energies for the ring opening of cyclopentane and cyclopentyl cyanide is reasonably close to the established value for the cyano stabilization energy. This supports the assumption of a biradical mechanism.

An electron impact study of HCN elimination from indole by use of 13C labelling

AbstractThe study of the loss of HCN from the molecular ions of [2‐13C]indole and [3‐13C]indole shows that, to a good approximation, only the two carbon atoms of the pentagonal ring are involved in this fragmentation process, contrary to the behaviour of the H atoms; the C‐2 atom is eliminated predominantly, chiefly in the ion source (85–90%) and a little less in the metastable energy range (75–80%). The losses of 13CCH3˙ and C2H3˙ from the [MH12CN]+˙ ions of the two compounds suggest the occurrence of different structures, providing evidence for several mechanisms of HCN elimination.

Kinetics and mechanism of the thermal decomposition of cyclopentyl cyanide

AbstractThe thermal decomposition of cyclopentyl cyanide has been investigated in the temperature range of 905–1143 K using both conventional stirred‐flow reactor and very low‐pressure pyrolysis (VLPP) techniques. The results from both techniques are consistent. The main primary processes are HCN elimination to form cyclopentene: equation image and ring fragmentation to form vinyl cyanide plus propylene and ethylene plus cyanopropenes: equation image Under the experimental conditions cyclopentene undergoes further decomposition to cyclopentadiene plus hydrogen. There is evidence for conversion of some of the reactant to a solid residue, presumably polymer. From the stirred‐flow reactor results the following Arrhenius expressions were obtained: log k1(s−1) = (12.8 ± 0.3) − (65.6 ± 1.3)/θ and log k2(s−1) = (16.0 ± 0.3) − (80.0 ± 1.1)/θ, where θ = 2.303RT kcal/mol. Application of RRKM theory shows that the VLPP experimental rate constants are consistent with high‐pressure Arrhenius parameters given by log k1(s−1) = (12.8 ± 0.3) − (67.8 ± 2.5)/θ for HCN elimination, and log k4(s−1) = (16.3 ± 0.3) − (80.1 ± 2.0)/θ for the sum of the ring fragmentation pathways. The rate parameters for HCN elimination are in good agreement with previous VLPP studies of alkyl cyanides and with theoretical predictions. The difference in activation energies for the ring opening of cyclopentane and cyclopentyl cyanide is reasonably close to the established value for the cyano stabilization energy. This supports the assumption of a biradical mechanism.

Thermolysis of complex cyanides, XV

The thermal decompositions of K2[Fe(CN)4 L]·4 H2O, H2[Fe(CN)4 L] and H[Fe(CN)L](L=1,1′-bipyridine, of 1,10-phenanthroline) were studied. The experimental results showed that the protonated ferrous complexes decompose with formation of HCN at lower temperature than the corresponding potassium salts. The decomposition of K2[Fe(CN)4 L] starts by removal of the ligand L. HCN elimination is followed by a redox reaction with formation of cyanogen in the case of H[FeIII(CN)4 L].

Substituent and Solvent Effects on HCN Elimination from 1-Aryl-1,2,2-tricyanoethanes

Abstract The elimination of HCN from 9-dicyanomethyl-fluorene (2), 1,1-diphenyl-1,2,2-tricyanoethane (3), and 2-phenyl-1,1,2-tricyanopropane (4) in anhydrous methanol has been studied and shown to occur via an (E l)anion mechanism. Elimination of HCN from 2 in acidic, buffered and MeO-/MeOH solutions have also been studied. Addition of water or benzene to the reaction medium shifts the mechanism to (E 1 CB)ʀ. Elimination of HCN from N,N-dimethyl-4-(1,1,2-tricyanoethyl) aniline (5) in anhydrous methanol occurs via an (E 1 cB)ʀ mechanism and the kinetics indicate that addition of HCN to the product alkene occurs. Activation parameters, isotope effects and solvent effects have been examined in an effort to obtain information about the nature of the transition states of these reactions.

The elimination of HCN (or HNC) from the molecular ions of some isomeric C 8H 7N compounds, studied by field ionization kinetic and kinetic energy release measurements

Field ionization kinetic measurements, coupled to D- and 13C-labelling experiments, have shown that, at times ⩽10 −9 s, HCN is eliminated from the molecular ions of benzyl cyanide via a formal 1,1-elimination. The benzylic carbon atom appears to participate in the loss of HCN at times ⩾10 −8 s. Collisional activation measurements suggest that the phenylcarbene ions resulting from the HCN elimination undergo a ring expansion to a seven-membered ring within 10 −5 s. It is further shown from kinetic energy release and field ionization kinetic measurements that the molecular ions of 7-cyanocycloheptatriene and of p-tolunitrile isomerize to a benzyl cyanide structure oprior to the loss of HCN.

Craquage thermique de l'aniline 1-14C

Thermal cracking of aniline 1- 14 C at atmospheric pressure at 900°C and a contact time of 2.5 sec breakdown mechanisms of the formation of benzene with an elimination of nitrogen, and formation of heterocyclic compounds and condensation products has been studied. Most of the degradation compounds are produced by a mechanism similar to the primary mechanism for the degradation of phenol: elimination of HCN with formation of inactive C 5 H 6 . The formation of nitriles is not negligible. On a étudié le craquage thermique de l'aniline à pression atmosphérique, à 900°C et pour un temps de séjour de 2.5 sec. L'utilisation d'aniline 1- 14 C a permis sinon de comprendre complètement, du moins d'éclaircir les différents mécanismes de rupture de cette molécule. Le mécanisme essentiel est la formation de benzéne avec une élimination globale d'azote. Nous avons également pu mettre en évidence des formations d'hétérocycles et de réaction de condensation. Nous avons également noté qu'une part non négligeable des produits de dégradation est produite par un mécanisme similaire à celui du mécanisme primaire de dégradation du phénol; à savoir une élimination d'acide cyanhydrique marqué et d'une structure en C 5 H 6 inactive. Enfin, la formation de nitriles n'est nullement négligeable.

Heavy Atom Kinetic Isotope Effects in HCN Elimination from Some Tricyanides in Methanol [1

Abstract Rates of HCN elimination from polycyanides N,N-dimethyl-4-(1,2,2-tricyanoethyl)-aniline (1), 9-cyano-9-dicyanomethyl fluorene (2), 1,1-diphenyl-1,2,2-tricyanoethane (3), and 2-phenyl-1,1,2-tricyanopropane (4) have been studied in methanol. Elimination from 1 occurs via (E 1 c B)R, mechanism. On the other hand olefin formation from 2-4 has been shown to occur via (E 1)anion pathway. Heavy atom kinetic isotope effects indicated that product stability is not the sole factor controlling the transition state geometries. Values of k12/k14 were found to be in the order 2 > 3 > 4 > 1 which implied transition states with more carbanion-like structure in the opposite direction. Solvent isotope effects and enthalpies of activation were also determined and discussed in terms of transition states geometries.

Nitrile elimination and hydrogen rearrangement upon electron impact in schiff base peptide esters

AbstractA series of Schiff base peptide esters were examined by gas chromatography mass spectrometry. Electron impact induced elimination of aryl nitriles (ArCN) from Schiff bases magnified image, where R, R′ …are amino acid sidechains formed from aromatic aldehydes and peptide esters was shown to be associated with formation of C‐terminal peptide fragments. Schiff base derivatives prepared from benzaldehyde and α‐deuterobenzaldehyde with several peptide esters indicated that aryl nitrile elimination was accompanied by H(D) transfer to the α‐C of the N‐terminal amino acid residue. Of the many Schiff base peptide esters of different aldehydes studied, HCN elimination of the type observed in some nonpeptide Schiff bases could only be found among N‐methyl pyrrolemethylidene derivatives.