Addition reactions of heterocycles—IV : Indoles and nitrilimines

The reactivity of indole derivatives towards nitrilimines has been studied. Substituents at positions 1, 2 and 3 of the indole ring greatly affect the course of the reaction. 1,3-Dipolar cycloaddition products (3a,8a,dihydropyrazole-[3,4-b]-indole derivatives) and non-cyclic addition products (3-indolyl derivatives) were obtained depending on these substituents. The structures reported were assigned on the basis of satisfactory analytical, spectroscopic and chemical data.     

Imino-bridged heterocycles. VII. N-aminobenzocycloheptapyridinimines

Condensation of anhydrous hydrazine with a variety of benzocycloheptapyridinones led to N-aminobenzocycloheptapyridinimines. Regiospecific ring closures occurred in all the systems investigated.     

Addition reactions of heterocycles. VI. Reactions of 1,2-dimethylpyrrole and 1-methyl-2-carbomethoxypyrrole with nitrilimines

Addition reactions of 1,2-dimethylpyrrole and 1-methyl-2-carbomethoxypyrrole with C-acetyl-N-phenylnitrilimine, have been investigated. 1,2-Dimethylpyrrole gives three different types of adducts: i.e. bis-cycloadducts (Vc) and (VIc), spirocycloadduct (IX), and non cyclic bis-adduct (XII). On the other hand, 1-methyl-2-carbomethoxypyrrole gives the bis-cycloadduct (VIb) only. Compound XII arises probably through a double 1,3-addition reaction, whereas the formation of cycloadducts Vc, VIc, and IX depends on the substituents present at C₂ of the pyrrole ring and consequentially on the intermediary occurence of mono-cycloadduct (IIIc), its methylenic tautomer VII, VIc, and XL The behaviour of the cycloadducts towards heating or acidic treatment showed a termal cleavage of the pyrazoline ring and acidic cleavage of the pyrrolidine ring.     

Fused-s-triazino heterocycles. VII. 1,3,5,7,9b-Pentaazaphenalene and 1,3,4,6,8,9b-hexaazaphenalene

Cyclization of 2,6-diaminopyrazine to two new heterocyclic ring systems, 1,3,5,7,9b-pentaazaphenalene and 1,3,4,6,8,9b-hexaazaphenalene is reported.     

Addition reactions to chiral aziridine-2-carboxaldimine toward various enantiopure nitrogen-containing heterocycles

Chiral (2R,1′R)-(1′-phenylethyl)aziridine-2-carboxaldimine was utilized as a nitrogen-containing starting substrate for the preparation of various enantiopure nitrogen-containing heterocycles. The additions of nucleophiles including organomagnesium reagents, cyanotrimethylsilane and ketene acetal to the chiral (2R,1′R)-(1′-phenylethyl)aziridine-2-carboxaldimine proceeded in highly stereoselective manner via chelation controlled transition states. Subsequent treatment of adducts with triphosgene and NaH yielded 5-substituted-4-chloromethylimidazolidin-2-ones. This imine was also served as either aza-diene or aza-dienophile with olefin or diene to provide hetero-Diels-Alder adducts 2-aziridinylpiperidines or 1,2,3,4-tetrahydroquinolines.     

Microwave-Assisted Conjugate Addition of Pyrrole on Electron-Deficient Nitro-Olefins

Michael addition of pyrrole to β-nitrovinyl compounds were carried out using microwave methodology. Monosubstituted pyrroles were obtained selectively in a major amount. Formation of novel product obtained during one of the reactions was explained by the double addition to nitrostyrene.     

Recyclization reactions of heterocycles

The direction of recyclization during hydrazination of isoquinolinium salts is practically independent of the substituent attached to nitrogen and the reaction conditions and leads to compounds with an N-aminoisoquinoline structure.See [1] for communication XIV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 961–965, July, 1974.     

Recyclization reactions of heterocycles

2-Thioxo-4-oxazolidone and thiazolidines containing heteroatom substituants (O, S, and NH) in the 2 and 4 positions are converted to benzimidazole derivatives on reaction with o-phenylenediamine. The direction of these recyclizations depends on the nature of the heteroatom substituents in the 2 and 4 positions of the heteroring.See [1] for communication XX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 666–668, May, 1978.     

Recyclization reactions of heterocycles

2,5-Dimethyl-1,3,4-oxa- and -1,3,4-thiadiazoles are recyclized to 2,5-dimethyl-4-amino-1,2,4-triazole on reaction with hydrazine. Recyclization occurs with greater difficulty and only with oxadiazole in the case of alkylhydrazines. Nitration of 2,5-dimethyl-4-amino-1,2,4-triazole gives its N-nitroamino derivative.See [1] for communication XVIII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 853–855, June, 1976.     

Synthesis of new fundamental heterocycles. Part VII. Synthesis of 2-azaxanthene

2-Azaxanthone ( 5 ) has been conveniently prepared by condensation of the morpholine enamine of 1-benzyl-4-piperidone witli salicylaldehyde followed by chromium trioxide oxidation and subsequent aromatization. Lithium aluminum hydride reduction of 5 afforded the new fundamental heterocycle 2-azaxanlhene.     

Pyrrole macrocyclic ligands for Cu-catalyzed asymmetric Henry reactions

New chiral perazamacrocycles containing four pyrrole rings have been synthesized by the [2+2] condensation of (R,R)-diaminocyclohexane and 5,5'-(alkane-2,2-diyl)bis(1H-pyrrole-2-carbaldehydes). These macrocycles, differing for the alkyl/aryl meso-substituents, were used as ligands in the copper-catalyzed Henry reactions of aromatic and aliphatic aldehydes with nitroalkanes. In the optimized experimental conditions, the condensations of nitromethane and aromatic and aliphatic aldehydes in the presence of catalytic amounts of copper diacetate and methyl-substituted macrocyclic ligand (2:1 ratio) in ethanol at room temperature provided products often with high enantiomeric excesses (up to 95% ee). The positive influence of the macrocyclic structure on the efficiency/enantioselectivity of the catalytic system was demonstrated by comparison with the outcomes of Henry reactions performed using analogous macrocyclic ligands (trianglamines) and open-chain ligands derived from (R,R)-diaminocyclohexane.     

Ylides of heterocycles. VII.. I-, N-, P- and S-ylides of pyrimidones

The reaction of pyrimidone derivatives 1a-d with iodosobenzene prepared in situ from diacetoxyiodobenzene or dichloroiodobenzene afforded the iodonium-ylides 2a-d in good yields. Their thermal rearrangement produced 5-iodo-4-phenoxy-pyrimidin-6(1H)-ones 3a-c . Reductive deiodination of 3 gave the corresponding 4-phenoxypyrimidin-6(1H)-ones 4a-c . Acid catalized treatment of the iodonium-ylides 2a-d with nucleophiles such as pyridine, nicotinamide, isoquinoline, or triphenylphosphine produced the corresponding N- or P-ylides 7, 8, 9 , and 10 , respectively. The thiophanium-ylides 11a,c were obtained from the iodonium-ylides 2 without the use of a catalyst. The pyridinium-ylides 7 have been also prepared from the 5-halopyrimidones 5 or 6 which in turn could be obtained from the reactive iodonium-ylides 2 with hydrochloric or hydrobromic acid, respectively.     

Quantum-chemical interpretation of recyclization reactions. 10. Photoisomerization of six-membered heterocycles

Singlet photoisomerizations of a number of six-membered heterocycles have been described on the basis of the index approach in the framework of the coupled variant of perturbation theory for a one-electron transition density matrix in the Pariser-Parr-Pople method.For Communication 9, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 357–363, March, 1986.     

Mass spectral fragmentation patterns of heterocycles. VII . Reinvestigation of fundamental processes in phenothiazines

Electron impact induced fragmentation patterns of simple phenothiazines have been reinvestigated using metastable ion studies, exact mass measurements and deuterated derivatives. Secondary fragmentation processes involving ions m/e 198, 171, 167, 166, 154, 140 and 139 have been clarified. Mechanisms for the release of sulfur (SH· and CSH·) nitrogen (HCN and H₂CN·) containing fragments from phenothiazine molecular ion are proposed based on the deuterium content of the daughter ions obtained from 1,9-dideutenophenothiazine. A revised mechanism for the expulsion of ketene from 10-acetylphenothiazine is suggested based on the fragmentation pattern of the 1,9-dideuterioderivative. The composition of m/e 140 was determined by high resolution measurement to be C₁₀H₆N and not C₁₁H₇ as previously reported.     

Quantum-chemical treatment of recyclization reactions. 9. Photoisomerization of five-membered heterocycles

The photoisomerization of a number of five-membered heterocycles has been considered in the framework of the coupled variant of perturbation theory for a one-electron transition density matrix in the -electronic approximation of the MO-LCAO-SCF method.For report 8 see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 173–180, February, 1986.