Sulfur ylides

A keto-stabilized sulfur ylide, containing phthalazinedione fragment, was synthesized. During thermolysis, the ylide forms the product of intramolecular cyclization of pyrrolophthalazinedione structure. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2227–2229, November, 2007.     

Sulfonium ylides

The intramolecular cyclization of keto-stabilized sulfonium ylides obtained from β-alanine and containing various imide fragments was studied. On heating in toluene in the presence of PhCO₂H, ylides containing a phthalimide moiety are converted into indolizidine-2,6-dione derivatives, whereas those incorporating a 4-methyl-1,2,3,6-tetrahydrophthalimide or pyrrolidine-2,5-dione moieties do not undergo cyclization. For Part 6, see Ref. 1 Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2008–2012, November, 1997.     

Sulfur ylides 8.* synthesis of 5-methylthio-7,8-dihydro-4,8a-diazfluorene-6,9-dione

Intramolecular cyclization of ketostabilized sulfur ylide obtained from β-alanine and 2,3-pyridinedicarboxylic anhydride was studied. The structure of the reaction product, 5-methylthio-7,8-dihydro-4,8a-diazafluorene-6,9-dione, was established by X-ray diffraction analysis. For Part 7, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2376–2378, November, 1998.     

Sulfur ylides 15. Intramolecular cyclization of new keto-stabilized sulfur bis-ylide

New sulfur bis-ylide was obtained from 3-amino-3-phenylpropionic acid and pyromellitic dianhydride. Its intramolecular cyclization proceeds regioselectively, leading to 3,4,11,12-tetrahydro-2H,6H-indolizino[2,1-f]pyrido[2,1-a]isoindole derivative in 66% yield. Phosphorus bis-ylide of similar structure gives a cyclization product in 10% yield. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2394–2396, December, 2007.     

Heterocyclic Compounds with a Bridge Nitrogen Atom. 14. Cycloaddition of Acetylenedicarboxylic Acid Ester to 2-Chloro-N-phenacylpyridinium Ylide. Crystal Structure of Dimethyl Ester of 5-Chloro-3-(p-nitrobenzoyl)indolizine-1,2-dicarboxylic Acid

Derivative of 5-chloroindolizine is formed in the reaction of 2-chloro-1-(p-nitrophenacyl)pyridinium ylide with acetylenedicarboxylic acid dimethyl ester, the structure of which was demonstrated by X-ray diffraction analysis. According to data of ¹H NMR and mass spectra indolizine obtained undergoes an unusual intramolecular cyclization with the formation of benz[e]cycl[3.3.2]azine nucleus.     

New synthesis of the dihydroindolizinoquinoline system by intramolecular cyclization of sulfur ylide

An efficient method is proposed for obtaining the dihydroindolizinoquinoline system by intramolecular cyclization of keto-stabilized sulfonium ylide obtained from -alanine and quinoline-2,3-dicarboxylic acid anhydride.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1813–1816, December, 2004.     

Kinetics of the 1,5-dipolar cyclization of 2-Vinylpyridinium ylides to Indolizines. Determination of rate parameters by laser flash photolysis

Nanosecond laser flash photolysis (λ = 355 nm) of an aqueous solution of 3-chloro-3-p-chlorophenyldiazirine in isooctane produces a transient absorption at 310 nm due to the formation of the carbene. In the presence of 2-vinylpyridine, a second transient with a broad absorption band peaking at 520 nm grows in. This absorption is attributed to 2-vinylpyridinium ylide. The ylide decays with a lifetime equal to 33 µs at 25°C independent of the concentration of 2-vinylpyridine. As the ylide decays, there is a concomitant growth of an absorption at 330 nm, attributed to the formation of inodolizine. The activation parameters for the 1,5-dipolar cyclization of the ylide to indolizine were determined; E_a = 12.1 kcal mol^?1 and log A = 13.4. © 1994 John Wiley & Sons, Inc.     

New aromatizational transformations of 4-methyl-4-trichloromethyl-substituted 2,5-cyclohexadiene triphenylphosphonium and pyridinium ylides: Abstraction or 1,6-migration of the CCl3 group

4-methyl-4-trichloromethylcyclohexadiene triphenylphosphonium ylide obtained by treatment of (1-methyl-1-tricholoromethylcyclohexa-2,4-dien-4-yl)-triphenylphosphonium bromide with BuⁿLi in THF is stabilized by the abstraction of the CCl₃ group to give (p-tolyl)triphenylphosphonium cation, which was isolated as the corresponding hydroxide. Conversely, an analogous pyridinium ylide, obtained by treatment ofZ/E stereoizomericN-(1-methyl-1-trichloromethylcyclohexa-2,5-dien-4-yl)pyridiunium bromide with a base (piperidine in CD₂Cl₂, BuⁿLi in THF), at temperatures above −40 °C, undergoes a novel high-yield aromatizational skeletal rearrangement with migration of the CCl₃ group to position 2 of the heterocycle. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 386–388, February, 1997.     

Sulfur ylides. 10. Modified method for the synthesis of pyrrolizine- and indolizinediones

A modified method for the synthesis of derivatives of pyrrolizinedione and indolizinedione was proposed. The method is based on the intramolecular cyclization of keto-stabilized sulfur ylides generated in situ from diazo ketones and Me₂S in the presence of Rh₂(OAc)₄.     

A study of influence of temperature and <Emphasis Type="Italic">N</Emphasis>, <Emphasis Type="Italic">N</Emphasis>-acyl protected keto ylides structure on their predominant transformations

The effect of temperature and keto ylides structure on preference of their intramolecular cyclization leading to N-containing heterocyclic compounds or linear products formation has been investigated at the B3LYP/6-31G(d,p) level of theory. It has been determined that the thermodynamic advantage of the cyclization reactions of ylides increases with temperature, while Gibbs free energies of linear products formation reactions depend insignificantly on temperature. The Wittig and the Corey–Chaykovsky reactions are least probable in the case of the sulfonium and ammonium ylides considered. However, for phosphonium ylides the Wittig reaction must be considerably preferable in comparison with other routes, while behavior of the arsonium ylides is predicted to be more complex. Research of S-ylides transformations shows that formation of methylthio-substituted heterocycles with five-, six- or seven- membered rings is possible from a thermodynamic standpoint, while conversion of the corresponding ylide to a four-membered heterocycle is disadvantageous. Presence of a methyl substituent and its position in the ylide carbon chain depends ambiguously on the behavior of sulfur keto ylides.     

Synthesis of 4,6-dinitro-2-trihalogenomethyl-2,3-dihydrobenzo[b]furans

A method for the synthesis of previously unknown 4,6-dinitro-2-trihalogenomethyl-2,3-dihydrobenzo[b]furans has been elaborated. The method is based on condensation of 2,4,6-trinitrotoluene with fluoral or chloral in the presence of K₂CO₃ with subsequent intramolecular cyclization of the resulting 2-picryl-1-(trihalogenomethyl)ethanols. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 569–570, March, 2000.     

Reactions of alkyl acetone-1,3-dicarboxylates with cyanamide and benzoylcyanamide

The reactions of cyanamide with dialkyl acetone-1,3-dicarboxylates in the presence of nickel acetylacetonate afforded alkyl 2-amino-4-hydroxy-6-oxo-1,6-dihydropyridine-3-carboxylates. The same compounds were obtained by intramolecular cyclization of adducts of acetone-1,3-dicarboxylates with benzoylcyanamide under the action of sodium alkoxides. Dedicated to Academician N. K. Kochetkov on the occasion of his 90th birthday. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1304–1306, May, 2005.     

Intramolecular cyclization ofN-acetyl-6-(cyclopent-1-enyl)-2-methylaniline

N-Acetyl-6-(cyclopent-1-enyl)-2-methylaniline underwent intramolecular cyclization in the presence of HCl in CH₂Cl₂ at 20°C to form 2,8-dimethylspiro[cyclopentane-1,4′-4′H-3,1-benzooxazine] in quantitative yield. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 398–400, February, 1999.     

Quantum chemical study of the effect of N,N-acyl group nature on the structure and Gibbs free energy of the sulfur ketoylides and products of their transformations

With the purpose to study the effect of the nature of the imido-group of N,N-acyl-protected β-methyl-substituted keto-stabilized sulfonium ylides on the formation of methylthiopyrrolisinediones by cyclization, the structure features of these ylides are investigated by ab initio methods. The imido-group nature is shown to insignificantly affect in most cases the structure and the relative free energy of conformers of the ketoylides in question and the products of a cyclization reaction with their participation. The energy difference between the anti-peri-planar and syn-clinal orientation of nitrogen atoms in the imido-group and ylide carbon atom is negligible. The latter orientation is necessary for the reaction of intramolecular cyclization to proceed because in this case carbon atoms between which the bond forms are drawn together. The structure of cyclic pentanomial N,N-acyl group slightly affects the calculated values of Gibbs free energy of sulfur ketoylide reactions, and a temperature increase promotes the intramolecualr cyclization reactions. Wittig and Corey-Chaykovsky reactions typical of ylides are the least thermodynamically favorable for the sulfonium ketoylides under study.     

Cascade reactions of nitrogen-and phosphorus-containing ylides with methyl diazoacetate and in situ generated diazocyclopropane

Reactions of pyridinium or phosphorus ylides with diazo esters are multistep processes. The first step is covalent bonding between the ylide C atom and the terminal N atom. This is followed by elimination of the ylide-forming molecule and successive addition of one or two ylide fragments. Depending on the nature of the starting reagents, this type of transformations leads to novel polyfunctional phosphorus ylides or, with pyridinium ylides, to polyalkyl 3,4(4,5)-diazaalkadienetri-or tetracarboxylates. A reaction of the in situ generated diazocyclopropane with methyl triphenylphosphoranylideneacetate stops at the first step, giving a cyclopropylazo-containing ylide. Reactions of the latter with acyl chlorides yield six-membered heterocyclic betaines with a triphenylphosphonium substituent. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 108–113, January, 2006.     

Cyclization ofN-acetyl-ortho-cycloalkenylanilines on treatment with bromine andN-bromosuccinimide

The reaction ofN-acetyl-2-(cyclohex-1-enyl)aniline with Br₂ orN-bromsuccinimide at 20°C is accompanied by intramolecular cyclization to give brominated 3,1-benzoxazines or 4-acetyl-(3-bromo-5-methyl-1,2,3,3a,4,8b-hexahydrocyclopenta[b]indole. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 118–120, January, 2000.     

Cyclization ofN-acetyl-ortho-cycloalkenylanilines on treatment with bromine andN-bromosuccinimide

The reaction ofN-acetyl-2-(cyclohex-1-enyl)aniline with Br₂ orN-bromsuccinimide at 20°C is accompanied by intramolecular cyclization to give brominated 3,1-benzoxazines or 4-acetyl-(3-bromo-5-methyl-1,2,3,3a,4,8b-hexahydrocyclopenta[b]indole. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 118–120, January, 2000.     

A new intramolecular transformation of aromatic nitroso oxides

The possibility of intramolecular interaction of a nitroso oxide group with an aromatic ring is investigated at the UB3LYP/6-311+G(d,p) and G3MP2B3 levels of theory for a wide series of aromatic nitroso oxides. It is found that this reaction leads to the formation of a dioxazole cycle, its subsequent decay resulting in opening of the benzene ring and formation of nitriloxide and carbonyl functional groups. The activation enthalpy of the transformation of phenylnitroso oxide is 75.1 kJ/mol. It is shown that various sub-stituents at ortho-position (with respect to the nitroso oxide fragment) considerably lower the activation barrier of the investigated transformation, particularly in case of o,p-dimethoxyphenylnitroso oxide ΔH ^≠ = 43.7 kJ/mol. It is concluded that in the case of polyaromatic nitroso oxides, for which intramolecular cyclization is more typical (ΔH ^≠ ∼ 50 kJ/mol), a factor favoring the attack on the ortho-carbon atom is the stabilization of the product’s diene group due to its inclusion in the polyaromatic system. It is established that sum of these effects leads to a low activation barrier for the transformation of nitroso oxide that forms during the photooxidizing of 2-azido-1-methoxyphenazine, ΔH ^≠ = 19 kJ/mol. It is proposed that due to the low activation energy of some nitroso oxides, their intramolecular cyclization may be the primary channel of their unimolecular decay.     

Intramolecular cyclization of ketene containing both acyl andN-alkylimidoyl substituents. Synthesis and crystal and molecular structure of 3-benzoyl-5-phenyl-2H,4H-furo[3,2-c] isoquinolin-2-one

Thermal decarbonylation of 1-benzyl-4,5-dibenzoyl-2,3-dihydropyrrole-2,3-dione yields benzoyl[N-benzyl(phenylglyoxalimidoyl)]ketene. The latter undergoes intramolecular cyclization to 3-benzoyl-5-phenyl-2,3,4,5-tetrahydrofuro[3,2-c]isoquinolin-2-one. Which is oxidized to 3-benzoyl-5-phenyl-2H,4H-furo[3,2-c]isoquinolin-2-one under the reaction conditions. The crystal and molecular structure of the title compound was studied by X-ray structural analysis. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 563–565, March, 1997.     

Molecular and crystal structure of 5Z-carboxymethylene-2-chloro-4,4-dimethoxy-3-N,N-dimethylaminocyclopent-2-en-1-one

In the crystal, the 5Z-carboxymethylene-2-chloro-4,4-dimethoxy-3-N,N-dimethyl-aminocyclopent-2-en-1-one molecule has an intramolecular hydrogen bond (stabilized in the chelate form) between the proton of the carboxy group and the oxygen atom of the keto group. The methoxy groups are in an antiperiplanar conformation and are synclinal with respect to the dimethylamino group and the double bond of the carboxylmethylene fragment. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1979–1981, November, 1997.