One-N, six-membered heterocyclic carbene complexes and the remote heteroatom concept

A whole library of six-membered N-heterocyclic carbene complexes of Ni(ii) and Pd(ii) were prepared by oxidative substitution. In some of these compounds the heteroatom occurs in a position distant from the carbene donor atom. Combined structural and physical data, especially (13)C NMR results, indicate carbene character in such ligands. DFT quantum mechanical calculation at the RI-BP56/SVP level allowed the extraction of valuable chemical information predicting that rNHC (r = remote) ligands would bond more strongly than their nNHC (n = normal) isomers. This result is also corroborated by calculations on the metal complexes themselves. Orbital overlap (mainly sigma) follows the order N(2)HC(5) < nN(1)HC(6) < rN(1)HC(6) when ligands derived from halo-imidazolium and halo-pyridinium salts are compared. In C-C coupling catalysis using Pd(ii) and Ni(ii) complexes, the simple one-N, six-membered carbene complexes are superior to simple two-N, five-membered examples but clear differentiation between nNHC and rNHC precatalysts in the former family, is not always possible.     

A convenient method for the synthesis of six-membered heterocyclic enaminones

Enaminones are widely employed in the synthesis of heterocycles, however heterocyclic enaminones and their use in the synthesis of more complex systems have been less studied. The reaction between 4-chloroacetylacetate and aliphatic or aromatic 1,2-aminoalcohols, 1,2-aminothiols or 1,2-diamines, yields in one pot a six-membered 1,4-heterocyclic system containing the enaminone moiety.     

Latent ruthenium carbene complexes with six-membered N- and S-chelate rings

New ruthenium carbene complexes with chelating N- and S-benzylidene ligands were synthesized by the reactions of second- and third-generation Grubbs catalysts with ortho-vinylbenzyl-substituted amines or sulfides. These complexes were shown to exhibit catalytic activity in ring-opening metathesis polymerization and ring-closing metathesis.     

过渡金属卡宾配合物:VIII. 四羰基[乙氧基(芳基)卡宾]铁配合物的方便合成法

五羰基铁, Fe(CO)~5(1), 与芳基锂(ArLi)在乙醚中于低温下反应, 所生成的酰羰基锂中间体在水溶液中于0℃用 Et~3OBF~4烷基化, 制得六个标题配合物(co)~4Fec(OC~1H~5)Ar(Ar:C~6H~5, 2;o-CH~3C~6H~4,3;p-CH~3C~6H~4, 4;p-CH~3OC~6H~4,5;C~6Cl~5,6;p-CF~3C~6H~4,7). 当用p-CF~3C~6H~4Li作为亲核试剂与1 反应时, 除生成7外, 还获得副产物对三氟甲基苯丙酮,p-CF~3C~6H~4COC~2H~5(8)。     

Reactions of 1,2-bis(trifluoroacetyl)benzene with nucleophiles leading to heterocyclic compounds

The reaction of 1,2-bis(trifluoroacetyl)benzene (II) with ammonia, hydrazine, hydroxylamine and L-alanine has been investigated and the resulting heterocyclic compounds fully characterized on the basis of spectral data. The reaction of II with $\text{o}$-aminophenol and $\text{o}$-phenylenediamine led to the formation of tetracyclic compounds XI and XII respectively. The structure of compound XII has been further supported by single crystal X-ray crystallography. Our studies reveal the potential of the diketone II as a valuable synthon for the synthesis of a variety of heterocyclic systems with trifluoromethyl substituents.     

Reactions of the 1-ferrocenyl-1,3-diphenylallyl cation with nucleophiles

Conclusion The reactions of 1-ferrocenyl-1,3-diphenylallyl cation with nucleophiles have been studied. In most cases they take place at the secondary carbon cation center; products of reaction at the tertiary center are found only in the case of small nucleophiles (MeO^–, OH^–). The data are evidence for the importance of steric factors, and also show that the ratio of reaction products at the -and -positions does not directly reflect charge distribution in the 1-ferrocenylallyl system.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2769–2776, December, 1986.     

A convenient route to heteronaphthacenes

Heteronaphthacenes 1 were prepared in two steps from 1,3-dihydrobenzo[c]thiophene 2,2-dioxide ( 4 ) and dienophiles 2 via convenient high-temperature Diels-Alder reactions.     

Reactions of nickel—carbene complexes generated from nickelacycle complexes

Nickel carbene species, generated from nickelacyclobutane complexes, reacted with hydrogen and carbon monoxide to give methane and ketene, respectively.     

N-H Insertion reactions of rhodium carbenoids. Part 5: A convenient route to 1,3-azoles

Dirhodium(II) carboxylate catalysed reaction of diazocarbonyl compounds 2 in the presence of primary amides 1 results in the formation of α-acylaminoketones 3 (12 examples) by N-H insertion reaction of the intermediate rhodium carbene. The 1,4-dicarbonyl compounds 3 are readily converted into structurally diverse oxazoles 4 (11 examples) by cyclodehydration, thiazoles 5 (10 examples) by treatment with Lawesson's reagent, or imidazoles 6 (2 examples) by reaction with ammonia or methylamine.     

A convenient route to new phenyltetrahydroindolizines

Synthesis of new 6-(4-chlorophenyl)-5,6,7,8-tetrahydroindolizines was achieved starting from 4-amino-3-(4-chlorophenyl)butyric acid (Baclofen). The chemical pathway, involving a Clauson-Kaas reaction and a subsequent cyclization, led to an iminium salt whose reactivity was studied.     

A highly regioselective reaction of N-fluoropyridinium salts with stabilized sulfur,oxygen, and nitrogen nucleophiles: A convenient route to 2-substituted pyridines

2-Substituted pyridines are efficiently obtained by the reactions of N-fluoropyridinium tetrafluoroborate or triflate with anions derived from benzenethiols, phenols, azoles, cyanamide, and with azide anion. The results are consistent with a nucleophile addition at the position 2 of the N-fluoropyridinium cation as the major reaction pathway.     

Cross-coupling of E,E-1,4-diiodobuta-1,3-diene with nucleophiles catalyzed by Pd or Ni complexes: a new route to functionalized dienes

E,E-1,4-Diiodobuta-1,3-diene can enter into cross-coupling reactions with carbon- or other element-centered nucleophiles in the presence of Pd or Ni complexes as catalysts. Convenient procedures were developed for the stereoselective synthesis of E,E-1,4-dialkenylbuta-1,3-dienes, dienyl-1,4-bisphosphonates, E,E-1,4-bis(diphenylphosphino)buta-1,3-diene, E,E-1,4-diphenylbuta-1,3-diene, and E,E-1,4-bis(thiophenyl)buta-1,3-diene.     

A convenient semisynthetic route to hypericin

Summary A semisynthetic route to produce hypericin was established usingCortex frangulae as the starting point. The emodin isolated from it easily and in good yield was reduced to emodin anthrone by means of SnCl₂. The latter was reacted via a known oxidative dimerization and photocyclization reaction into hypericin.

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Ein bequemer semisynthetischer Zugang zu Hypericin

Zusammenfassung Eine semisynthetische Route zur Darstellung von Hypericin unter Verwendung vonCortex frangulae als Ausgangsmaterial wurde erarbeitet. Das daraus einfach und in guten Ausbeuten isolierte Emodin wurde mit Hilfe von SnCl₂ zu Emodinanthron reduziert. Letzteres wurde dann über eine bekannte oxidative Dimerisierung und Photocyclisierung zu Hypericin umgesetzt.

     

I2/TBHP-mediated domino process: a convenient route to 1,3-oxazole derivatives

A practical and simple synthesis of 2,5-disubstituted oxazoles was developed via a TBHP (tert-butyl hydroperoxide)/I₂-mediated domino strategy. The reaction proceeds in series, giving rise to the formation of an intermolecular C–N bond and an intramolecular C–O bond, which yield oxazole derivatives simultaneously. The reaction gave the desired products from readily available substrates under mild conditions.     

Reactions of heterocyclic cations with nitrogen-containing nucleophiles. 12. Reaction of pyrylium salts with azomethines

The reaction of pyrylium salts with azomethines leads to the formation of styrylpyrylium, styrylpyridinium, and 4-arylbenzylaminopyrylium salts. The reaction of the latter with ammonia and amines gave pyridines and pyridinium salts with a tertiary amino group as a substituent.See [1] for Communication 11.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 465–468, April, 1982.