The synthesis of β-carboline derivatives-II A synthesis of some benz-indolo[2,3-a]pyridocolinium salts, including sempervirine

A novel synthetic method for β-carboline derivatives, described in the preceding paper, is now applied to the syntheses of 6,7-dihydro-12H-benz[f]indolo[2,3-a]pyridocolinium salt, 8,9-dihydro-14H-benz[h]indolo-[2,3-a]pyridocolinium salt and sempervirine. In the course of synthesis of sempervirine, 2-[2-(3-indolyl)ethyl]-3-chloro-5,6,7,8-tetrahydro-isoquinolinium bromide is obtained as an intermediate, lending strong support for the mechanism previously proposed.     

Synthesis and tautomerization of benzo[cd]azulen-3-ones

This report describes a type of tautomerization reaction that proceeds via isomerization of π-bonds across the azulene moieties of tricyclic benzo[cd]azulen-3-ones. The reaction mechanism shows similarities to an elimination reaction that was recently developed in our group. Furthermore, the facile four-step syntheses of the benzo[cd]azulen-3-ones, the starting materials for the tautomerization reactions, and computational analyses of the tautomerization reaction are included.     

The addition of benzyne to azulene

The title reaction afforded the Diels-Alder adduct 4b,10-ethenobenz [ ]azulene (4), while an analogous reaction involving 5,6-dichloroazulene gave the 6,7- and 7,8-dichloro-derivatives of (4). Treatment of (4) with 3,6-di(pyridin-2-yl)- -tetrazine yielded benz[ ]azulene.     

Diels-alder cycloaddition of tetrachlorothiophene-S,S-dioxide to azulene

The cycloaddition of tetrachlorothiophene-S,S-dioxide to azulene occurs across the 1- and 2-positions to give 1,2,3,4-tetrachlorobenz[a]azulene.     

Palladium-catalyzed reaction of methyl 5-amino-4-chloro-2-methylthiopyrrolo[2,3-<Emphasis Type="Italic">d</Emphasis>]-pyrimidine-6-carboxylate with arylboronic acids. Synthesis of 1,3,4,6-tetraazadibenzo[<Emphasis Type="Italic">cd,f</Emphasis>]-azulene heterocyclic system

Densely substituted methyl 5-amino-4-aryl-7-methyl-2-methylthio-7H-pyrrolo[2,3-d]pyrimidine-6-carboxy- lates were synthesized by the palladium-catalyzed cross-coupling reaction of methyl 5-amino-4-chloro-7-methyl-2-methylthio-7H-pyrrolo[2,3-d]pyrimidine-6-carboxylate with arylboronic acids using Pd(OAc)₂/dicyclohexyl(2-biphenyl)phosphine/K₃PO₄ as a catalyst system. Reaction of methyl 5-amino-4-chloro-7-methyl-2-methylthio-7H-pyrrolo[2,3-d]pyrimidine-6-carboxylate with 2-formylphenyl- boronic acid led to a novel heterocyclic system – 1,3,4,6-tetraazadibenzo[cd,f]azulene.     

Novel synthesis of benzalacetone analogues of naphth[a]azulenes by intramolecular tropylium ion-mediated furan ring-opening reaction and X-ray investigation of a naphth[1,2-a]azulene derivative

[reaction: see text] Benzalacetone analogues of naphth[1,2-a]azulene (8), naphth[2,1-a]azulene (13), and naphth[2,3-a]azulene (18) were synthesized from 2-(5-methyl-2-furyl)-1-tropylionaphthalene (7), 1-(5-methyl-2-furyl)-2-tropylionaphthalene (12), and 2-(5-methy-2-furyl)-3-tropylionaphthalene (17), respectively. The synthetic method is based on furan ring-opening reaction by the intramolecular electrophilic attack of a tropylium ion. Single-crystal X-ray work on the naphth[1,2-a]azulene derivative (8) revealed that its tetracyclic system exhibited deformation from planarity similar to that of benzo[c]phenanthrene (tetrahelicene). A centrosymmetric associated dimer structure, just like the molecules of carboxylic acids but via C=O...H-C hydrogen bonds, was found in the crystal. Reduction of bond-length alternation in the seven-membered ring was also found.     

Thermal reduction of 7H-benz[d,e]anthracen-7-one and related ketones under hydrogen-transfer conditions

In the presence of hydrogen donor solvents and at elevated temperatures, aromatic ketones can be selectively deoxygenated to the corresponding hydroaromatic compounds. The kinetics for reduction of 7H-benz[d,e]anthracen-7-one (benzanthrone, 6) into 7H-benz[d,e]anthracene (benzanthrene, 1) in 9,10-dihydroanthracene (3) solvent has been investigated in detail. The relatively slow hydrogenation of 6 is due to reversibility of the initial hydrogen-transfer step according to a reverse radical disproportionation (RRD). The dynamics could well be rationalized using the energetics of species computed by density functional theory (DFT). The application of hydrogen donors such as 1 as a hydrogen-transfer agent, although favorable in terms of a low benzylic carbon-hydrogen bond dissociation enthalpy, is limited due to the slow self-hydrogenation, which in case of 1 gives 5,6-dihydro-4H-benz[d,e]anthracene (7).     

Novel salicylaldehyde-based mineral-supported expeditious synthesis of benzoxazin-2-ones

One-pot montmorillonite K-10 clay supported reactions of either salicylaldehyde/2-hydroxyacetophenone hydrazones and aryl-/alkylureas or salicylaldehydes/2-hydroxyacetophenone and 4-aryl-/alkylsemicarbazides expeditiously yield 3,4-dihydro-4-hydrazino-2H-benz[e]-1,3-oxazin-2-ones (9) via cycloisomerization of the intermediate salicylaldehyde/2-hydroxyacetophenone 4-aryl-/alkylsemicarbazones (5) under solvent-free microwave irradiation. Under the same conditions, hydrazines (9) readily underwent reductive dehydrazination on alumina-supported copper(II) sulfate to furnish 2H-benz[e]-1,3-oxazin-2-ones (10).     

Synthesis,Crystal Structure and Characterization of 6-(p-tolyl)-6-H-Decachlorobenzo[cd]pyrene

A new perchlorinated fused compound, 6-(p-tolyl)-6H-decachloro-benzo[cd]-pyrene 1, was synthesized with solvothermal reaction,a novel approach developed in our group. 1 is an interesting molecule for it is similar in structure to chlorinated fragment molecules of fullerenes^[1]. Besides, its homologues such as 6-methyl-6H-benzo[cd]pyrenes, 6-methoxycarbonyl-6H-benzo[cd]pyrene and 6-mesyloxyl-6H-benzo[cd]pyrene[2] have been synthesized as parent hydrocarbons of benzo[cd]pyrenyl system, which were investigated for its NBMO properties^[3].     

Investigation of the products of the reaction of epichlorohydrin with aromatic amines

The action of hydrogen halides on 7a,8-dihydro-7H-azirino[1,2-]benz[g]indole gives 2-halomethyl-2,3-dihydro-1H-benz[g]indoles and 3-halo-1,2,3,4-tetrahydrobenzo[h]quinolines, which were converted to the corresponding N-nitroso derivatives and then to the isonitroso derivatives. 2-(Benzoxymethyl)-2,3-dihydro-1H-benz[g]indole hydrohalides were obtained by heating 1-benzoyl-2-halomethyl-2,3-dihydro-1H-benz[g]indoles. The reaction of 3-halo-1,2,3,4-tetrahydrobenzo[h]quinolines with thionyl chloride at room temperature gives 3-halo-6-chloro-1,2,3,4-tetrahydrobenzo[h]quinolines, while refluxing with thionyl chloride gives 6-chlorobenzo[h]quinoline.See [1] for communication XVI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 342–346, March, 1973.     

A Novel Synthesis of 3-Amido-5-phenyl-benzazepin-2-one via an Intramolecular Amidoalkylation

A synthesis of N-(8-Methyl-2-oxo-5-phenyl-2,3-dihydro-1H-benz[b]azepin-3-yl)-benzamide 2 via an intramolecular amidoalkylation is described.     

Formation of Azulene‐Embedded Nanographene: Naphthalene to Azulene Rearrangement During the Scholl Reaction

Incorporation of a non‐hexagonal ring into a nanographene framework can lead to new electronic properties. During the attempted synthesis of naphthalene‐bridged double [6]helicene and heptagon‐containing nanographene by the Scholl reaction, an unexpected azulene‐embedded nanographene and its triflyloxylated product were obtained, as confirmed by X‐ray crystallographic analysis and 2D NMR spectroscopy. A 5/7/7/5 ring‐fused substructure containing two formal azulene units is formed, but only one of them shows an azulene‐like electronic structure. The formation of this unique structure is explained by arenium ion mediated 1,2‐phenyl migration and a naphthalene to azulene rearrangement reaction according to an in‐silico study. This report represents the first experimental example of the thermodynamically unfavorable naphthalene to azulene rearrangement and may lead to new azulene‐based molecular materials.     

Cyclopentadiene annulated polycyclic aromatic hydrocarbons: investigations of electron affinities

The adiabatic electron affinities of cyclopentadiene and 10 associated benzannelated derivatives have been predicted with both density functional and Hartree-Fock theory. These systems can also be regarded as benzenoid polycyclic aromatic hydrocarbons (PAHs) augmented with five-membered rings. Like the PAHs, the electron affinities of the present systems generally increase with the number of rings. To unequivocally bind an electron, cyclopentadiene must have at least two conventionally fused benzene rings. 1H-Benz[f]indene, a naphthalene-annulated cyclopentadiene, is predicted to have a zero-point energy corrected adiabatic electron affinity of 0.13 eV. Since the experimental E(A) of naphthalene is negative (-0.19 eV), the five-membered ring appendage contributes to the stability of the naphthalene-derived 1H-benz[f]indene radical anion significantly. The key to binding the electron is a contiguous sequence of fused benzenes, since fluorene, the isomer of 1H-benz[f]indene, with separated six-membered rings, has an electron affinity of -0.07 eV. Each additional benzene ring in the sequence fused to cyclopentadiene increases the electron affinity by 0.15-0.65 eV: the most reliable predictions are cyclopentadiene (-0.63 eV), indene (-0.49 eV), fluorene (-0.07 eV), 1H-benz[f]indene (0.13 eV), 1,2-benzofluorene (0.25 eV), 2,3-benzofluorene (0.26 eV), 12H-dibenzo[b,h]fluorene (0.65 eV), 13H-indeno[1,2-b]anthracene (0.82 eV), and 1H-cyclopenta[b]naphthacene (1.10 eV). In contrast, if the six-membered ring-fusion is across the C(2)-C(3) cyclopentadiene single bond, only a single benzene is needed to bind an electron. The theoretical electron affinity of the resulting molecule, isoindene, is 0.49 eV, and this increases to 1.22 eV for 2H-benz[f]indene. The degree of aromaticity is responsible for this behavior. While the radical anions are stabilized by conjugation, which increases with the size of the system, the regular indenes, like PAHs in general, suffer from the loss of aromatic stabilization in forming their radical anions. While indene is 21 kcal mol(-1) more stable than isoindene, the corresponding radical anion isomers have almost the same energy. Nucleus-independent chemical shift calculations show that the highly aromatic molecules lose almost all aromaticity when an extra electron is present. The radical anions of cyclopentadiene and all of its annulated derivatives have remarkably low C-H bond dissociation energies (only 18-34 kcal mol(-1) for the mono-, bi-, and tricyclics considered). Hydrogen atom loss leads to the restoration of aromaticity in the highly stabilized cyclopentadienyl anion congeners.     

The addition of benzocyclobutenylidene to benzene : The facile rearrangement of spiro[benzocyclobutene-1,7'-cyclohepta-1',3',5'-triene] to 9a,10-dihydrobenz[α]azulene

Thermal decomposition of the sodium salts of benzocyclobutenone tosylhydrazone and 2-methylbenzocyclobutenone tosylhydrazone in benzene affords 9a,10-dihydrobenz[α]azulene 4 and trans-10-methyl-9a, 10-dihydrobenz[α]azulene 3, respectively. A mechanism involving initially the addition of the carbene benzocyclobutenylidene, or its 2-Me derivative, to the benzene ring is postulated. A proposed intermediate in the reaction, spiro [benzocyclobutene 1,7' cyclohepta-1',3',5'-triene] 12 has been synthesised, and shown to give rise to 4 under the reaction conditions. The rate of rearrangement of 12 → 4 has been measured, and the activation energy determined: E_a = 125.9 ± O.8 KJmol^?1 and A = 1.38 × lO¹⁴sec^?1. The mechanism for the rearrangement must involve ring opening of the benzocyclobutene moiety of 12 to give an o- xylylene intermediate which is postulated to possess considerable diradical character. At 71.8 °, this ring opening is 2.7 × 10⁶ times faster than the ring opening of the parent benzocyclobutene molecule. The decomposition of the sodium salt of 2-(7' -cyclohepta-1',3',5' trienyl)benzaldehyde tosylhydrazone has also been investigated and is shown to yield 4a,10-dihydrobenz[α]azulene, 9,10-dihydrobenz[α]azulene and 8,9-benzotricyclo [5.3.0.0^2.10]deca-3,5,8-triene. A mechanism involving intramolecular 1,3-dipolar addition of a diazo grouping to a cycloheptatriene Π-bond, followed by decomposition of the resulting pyrazoline intermediate, is proposed.     

Syntheses based on 3H-benz[e]indole o-quinones

Some 4,5-dioxo-4,5-dihydro-3H-benz[e]indoles have been alkylated. The N-alkyl derivatives were used in the synthesis of 8-oxoindenol[2,1-b]pyrroles and 2-aminomethyl-3-methyl (and benzyl)-4,5-dioxo-4,5-dihydrobenz[e]indole.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 611–614, May, 1989.     

Formation of Azulene-Embedded Nanographene: Naphthalene to Azulene Rearrangement During the Scholl Reaction

Incorporation of a non-hexagonal ring into a nanographene framework can lead to new electronic properties. During the attempted synthesis of naphthalene-bridged double [6]helicene and heptagon-containing nanographene by the Scholl reaction, an unexpected azulene-embedded nanographene and its triflyloxylated product were obtained, as confirmed by X-ray crystallographic analysis and 2D NMR spectroscopy. A 5/7/7/5 ring-fused substructure containing two formal azulene units is formed, but only one of them shows an azulene-like electronic structure. The formation of this unique structure is explained by arenium ion mediated 1,2-phenyl migration and a naphthalene to azulene rearrangement reaction according to an in-silico study. This report represents the first experimental example of the thermodynamically unfavorable naphthalene to azulene rearrangement and may lead to new azulene-based molecular materials.     

Highly Efficient Photosensitization of Mesoporous TiO_2 Electrode with a Cyanine Dye

Dye-sensitized mesoporous TiO2 photoelectrochemical cell has attracted much interest for photoelectric conversion1,2. The most efficient charge transfer dye studied so far is Ru(dcbpy)2(NCS)2 (dcbpy=4, 4'-dicarboxy-2, 2'-bipyridine), with which IPCE of about unity has been achieved3. Considering the low cost, low toxicity, easy handling, non-metal complex dyes should also be right candidates. Here we report the highly efficient photosensitization of mesoporous TiO2 electrode with a nov…     

Dynamic equilibration of eta 1-carbene and eta 2-alkyne moieties within an alkynylcarbene dimanganese complex

The coordination of an additional [Cp(CO)2Mn] fragment to the alkyne linkage of an alkynylcarbene complex of the type Cp(CO)2Mn=C(R')C identical to CR" yields a highly fluxional molecule, in which the [eta 1-carbene] and [eta 2-alkyne] moieties are seen to exchange rapidly on the NMR time scale.     

Azulene–Naphthalene‐Type Rearrangements in Benz[a]azulene and Cyclohepta[b]indole

Flash vacuum pyrolysis (FVP) of benz[a]azulene yields phenanthrene and 2‐ethynylbiphenyl. FVP of cyclohepta[b]indole similarly yields phenanthridine and 2‐cyanobiphenyl. The reversibility of the reactions is demonstrated by FVP of 2‐ethynylbiphenyl and 2‐isocyanobiphenyl. All the observed reactions are in accord with the norcaradiene–vinylidene mechanism of the azulene–naphthalene rearrangement, whereas other proposed mechanisms are ruled out.     

Bonding modes of stanna-closo-dodecaborate: eta1(Sn) to eta3(BH) rearrangement reactions in zwitterionic stanna-closo-dodecaborate ruthenium complexes

Reaction of the stanna-closo-dodecaborate salt [Bu3MeN]2[SnB11H11] with the dimeric ruthenium complex [Ru2(mu-Cl)3(triphos)2]Cl (triphos = {MeC(CH2PPh2)3}) in refluxing acetonitrile yields the zwitterionic compound [Ru(SnB11H11)(MeCN)2(triphos)] (4) which has been characterized by single-crystal X-ray diffraction analysis and solid-state NMR spectroscopy. Refluxing the zwitterion in acetone leads to an eta1(Sn) to eta3(BH) rearrangement with formation of [Ru(SnB1)H11)(triphos)] (5) whose structure has been confirmed by X-ray diffraction and multinuclear NMR spectroscopy in solution and in the solid state. Furthermore, two isomeric zwitterions fac- and mer-[Ru(SnB11H11)(dppb)(MeCN)3] (6a, 6b) and their rearrangement reactions as well as their NMR properties are described.