Nickel(0)-mediated [2+2+1] cyclization reaction of chromium carbene complexes and internal alkynes

Alkyl, aryl, and heteroaryl chromium Fischer carbene complexes undergo Ni(0)-mediated [2+2+1] cyclization reaction with internal unactivated and electron-poor internal alkynes to yield highly substituted cyclopentadienes with complete regioselectivity in most cases. The intramolecular version of this cyclization has been accomplished with 1,8-diphenyl-1,7-octadiyne to produce indene derivatives. This three-component [2+2+1] cyclization represents a very uncommon process in the chemistry of Fischer carbene complexes.     

Synthesis of 3-substituted trans-2-oxadecalins and 1-substituted trans-2-oxahydrindanes

A study was carried out of the intramolecular cyclization of trans-1-methoxymethyl-2-(1-hydroxyalkyl)cyclohexanes and trans-1-methoxymethyl-2-(2-hydroxyalkyl)cyclohexanes by the action of acid chlorides of phosphorous, sulfurous and p-toluenesulfonic acids with the formation of 1-substituted trans-2-oxahydrindanes in low yields and 3-substituted trans-2-oxadecalins in high yields. A relationship has been established between the yields of the cyclization products and the nature of the halogenating agent. The cyclization does not proceed via an intermediate oxonium ion, but by means of an intermolecular electronic transition.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1865–1877, August, 1991.     

6-Substituted 2-(2-benzothiazolyl) [1, 2, 3] benzotriazol-1-oxides and the kinetics of their formation

6-Substituted 2-(2-benzothiazolyl) [1, 2, 3] benzotriazol-1-oxides were prepared by a base catalyzed cyclization reaction of 2-(4-substituted 2-nitrophenylhydrazino) benzothiazoles. Influence of substitution in position 4 on the cyclization reaction rate was followed and correlated with Hammett constants.     

Specific synthesis of 1,2- and 1,3-dialkylidenecycloheptanes by [3+2+2] cyclization of alkenyl Fischer carbene complexes and allenes

The 1,2- and 1,3-dialkylidenecycloheptane rings are specifically assembled from chromium alkenyl Fischer carbene complexes and allenes via [3+2+2] cyclization reactions. The former cycloadducts are obtained when the cyclization is performed in the presence of 1 equiv of [Ni(cod)2], while the [Rh(cod)Cl]2-catalyzed cyclization leads to the latter cycloadducts.     

Structurally novel Bi- and tricyclic beta-lactams via [2 + 2] cycloaddition or radical reactions in 2-azetidinone-tethered enallenes and allenynes

[reaction: see text] Thermolysis of beta-lactam-tethered enallenyl alcohols gave tricyclic ring structures via a formal [2 + 2] cycloaddition of the alkene with the distal bond of the allene, while the tin-promoted radical cyclization in 2-azetidinone-tethered allenynes proceeded to provide bicyclic beta-lactams containing a medium-sized ring. The access to cyclization precursors was achieved by regio- and stereoselective metal-mediated carbonyl allenylation of 4-oxoazetidine-2-carbaldehydes in an aqueous environment.     

Stereoselective synthesis of 2-deoxy-2-iodo-glycosides from furanoses. A new route to 2-deoxy-glycosides and 2-deoxy-oligosaccharides of ribo and xylo configuration

[reaction: see text] A general procedure for the stereoselective synthesis of 2-deoxy-2-iodo-hexo- and -hepto-pyranosyl glycosides from furanoses is reported. The proposed methodology provides a new route for accessing 2-deoxy-oligosaccharides. The procedure involves three reactions: Wittig-Horner olefination to give alkenyl sulfanyl derivatives, electrophilic iodine-induced cyclization to give phenyl 2-deoxy-2-iodo-1-thio-hexo-glycosides, and glycosylation. Protected furanoses 1, 3, and 6-11, which include examples of the four possible isomeric configurations of furanoses, were reacted with diphenyl phenylsulfanylmethyl phosphine oxide to give the alkenyl sulfanyl derivatives 2, 4, and 12-16. The iodine-induced cyclization of these compounds afforded the phenyl 2-deoxy-2-iodo-1-thio-glycosides 18, 20, and 22-27 with practically complete regio- and stereoselectivity. Products of 6-endo cyclization, in which the iodine at C-2 was in a cis relationship with the alkoxy at C-3, were almost exclusively produced. Better yields were obtained for compounds with a ribo or xylo configuration than for compounds with other configurations. Compounds 18, 20, and 22-27 were found to be efficient glycosyl donors in the glycosylation of cholesterol and glucopyranoside 29a, affording the corresponding 2-deoxy-2-iodo-glycosides and 2-deoxy-2-iodo-oligosaccharides with good yields and stereoselectivities. The glycosydic bond in the major isomers was always trans to the iodine at C-2.     

Comparative study of ring-chain isomeric transitions of 2-cyano-substituted benzamides and benzenesulfamides

The rate constants of cyclization and the constant of ring-chain equilibrium of N-isopropyl-2-cyano-substituted benzamide and benzamide and benzenesulfamide by the methods of PMR and IR spectroscopy, and it was shown that in the transition from 2-cyanobenzamides to 2-cyanobenzenesulfamides a sharp destabilization of the cyclic isomeric form is observed; however, the cyclization of 2-cyanobenzenesulfamides proceeds at a higher rate than the cyclization of 2-cyanobenzamides.     

One-pot cyclization of dilithiated nitriles with isothiocyanates and epibromohydrin. Synthesis of 2-cyano-1-(hydroxymethyl)cyclopropanes and 2-cyanomethylidene-4-(hydroxymethyl)thiazolidines

The cyclization of dilithiated nitriles with epibromohydrin afforded 2-cyano-1-(hydroxymethyl)cyclopropanes. 2-Cyanomethylidene-(4-hydroxymethyl)thiazolidines were prepared by one-pot cyclization of dilithiated nitriles with isothiocyanates and epibromohydrin.     

Synthesis of 2H-1,2-oxaphosphorin 2-oxides via Ag2CO3-catalyzed cyclization of (Z)-2-alken-4-ynylphosphonic monoesters

[reaction: see text]. Six new 2-ethoxy-2H-1,2-oxaphosphorin 2-oxides were synthesized with high regioselectivity in good yields via Ag(2)CO(3)-catalyzed cyclization of (Z)-2-alken-4-ynylphosphonic monoesters in CH(2)Cl(2) at room temperature. This cyclization of P-OH to substituted alkynes is reported for the first time. The products are a class of phosphorus heterocycles with potential use and are heretofore prepared with difficulty.     

Reaction of 1-Nitro-9,10-anthraquinone-2-carboxylic Acid with 2-Aminoethanol

1-Nitro-9,10-anthraquinone-2-carboxylic acid reacts with 2-aminoethanol to give 1-(2-hydroxy- ethylamino)-9,10-anthraquinone-2-carboxylic acid which undergoes intramolecular cyclization to 1,2,3,5,8,13- hexahydroanthra[1,2-e][1,4]oxazepine-5,8,13-trione on heating in acetic acid. Reactions of the cyclization product with amines result in cleavage of the seven-membered heteroring.     

Rhodium-catalyzed selective [2+2+2] cyclizations of 1,6-diynes with monoynes leading to isoindolines and isobenzofurans

<正>A highly efficient and selective[2+2+2]cyclization of diynes and monoalkynes was catalyzed by rhodium under room temperature in water/THF mixed solvent,affording isoindolines and isobenzofurans in good to excellent yields.The center atoms (N,O) in the diynes showed a significant effect for the cyclization.     

Synthesis of pyrazinyl compounds from glycerol and 1,2-propanediamine over Cu-TiO2 catalysts supported on γ-Al2O3

Cu-TiO₂ catalysts supported onγ-Al₂O₃ are prepared and used in glycerol cyclization with 1,2-propanediamine to produce pyrazinyl compounds including 6-hydroxymethyl-2-methylpyrazine,5-hydroxymethyl -2-methyIpyrazine,2,6-dimethylpyrazine and 2,5-dimethylpyrazine in a fixed-bed system.It is found that glycerol cylclization with 1,2-propanediamine gave a high total yield of pyrazinyl compounds（>80%） over Cu-Ti02/γ-Al₂O₃ catalyst,and cyclization was through the reactions between activated 1,2-propanediamine and the intermediates from glycerol dehydration and oxidation.In addition,the regioselectivity of the pyrazinyl compounds was mainly controlled by the steric hindrance of the substrates during the cyclization process.     

Photoinduced C-Br homolysis of 2-bromobenzophenones and Pschorr ring closure of 2-aroylaryl radicals to fluorenones

A variety of diversely substituted 2-aroylaryl radicals, generated by photoinduced homolysis of 2-bromoarylketones, is shown to undergo Pschorr cyclization to yield fluorenones in moderate to excellent yields. The photochemical results illustrate that the substituents in the two phenyl rings of the 2-bromobenzophenone skeleton exert a dramatic influence on the reactivity of the derived 2-aroylaryl radicals. The disubstitution by methoxy groups in the radical ring renders the aryl sigma-radical highly electrophilic and unreactive for hydrogen abstraction and cyclization. On the other hand, the substituents in the non-radical ring that strongly stabilize the hydrofluorenyl pi-radical, formed subsequent to the attack of the 2-aroylaryl radical on the non-radical ring, promote cyclization to furnish fluorenones in excellent isolated yields.     

A selective and convenient method for the synthesis of 2-phenylaminothiazolines

A series of 2-phenylaminothiazolines have been prepared from the corresponding N-(2-hydroxyethyl)-N'-phenylthioureas under mild reaction conditions using either thio-CDI (1,1'-thiocarbonyldiimidazole) or CDI (1,1'-carbonyldiimidazole) to promote the cyclization. This protocol provides the desired cyclization products in good yield with excellent selectivity. The scope and selectivity of this methodology are also described.     

Synthesis of 2-aminobenzoxazoles and 2-iminobenzoxazolines

The cyclization of sulfonamide derivatives of alkylated 2-hydroxyphenylthioureas in the presence of an ammoniacal solution of silver oxide gives 2-alkylaminobenzoxazole-5-sulfonamides or the corresponding 3-alkyl-2-alkyliminobenzoxazolines. Alkyl-substituted 2-aminobenzoxazole-5-sulfonamides were also obtained by the reaction of benzoxazolylthione with secondary amines and aniline.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 173–174, February, 1976.     

Heterocyclization of compounds containing diazo and cyano groups. 6. Theoretical and experimental investigations of cyclization of 2-cyano-2-diazoacetamides to 5-hydroxy-1,2,3-triazole-4-carbonitriles

A series of N-alkyl- and N-aryl-2-cyano-2-diazoacetamides was synthesized by the reaction of 2-amino-2-cyanoacetamides with sodium nitrite in hydrochloric acid. The mechanism of their heteroclectrocyclization to 5-hydroxy-1,2,3-triazoles was investigated kinetically and theoretically by the B3LYP/6-31+G^* method. The conclusion was made on the basis of the determined activation energy of the cyclization process. reaction parameters , and kinetic isotope effects, that there is a difference between the mechanisms of cyclization of the N-alkyl and N-aryl derivatives of 2-cyano-2-diazoacetamide; cyclization of the N-alkyl derivatives takes place by a monorotatory mechanism, while cyclization of the N-aryl derivatives takes place by a mechanism where one of the stages is heteroelectrocyclization of 2-diazoacetimidates.For Communication 5, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 26–41, January, 2000.     

Preparation and properties of 2-(4-arylamino-2-quinolyl) quinolines

2-Acetylquinoline o-arylcarbamoylanils were synthesized and converted to 2-(4-arylamino-2-quinolyl) qulnolines by intramolecular cyclization. The new compounds form colored complexes with copper (I).     

Gold-catalyzed reactions of 2-alkynyl-phenylamines with alpha,beta-enones

[reaction: see text] The gold-catalyzed reaction of 2-alkynyl-phenylamines with alpha,beta-enones represents a new general one-pot entry into C-3-alkyl-indoles by sequential reactions. Gold-catalyzed sequential cyclization/alkylation, N-alkylation/cyclization, or N-alkylation/cyclization/alkylation reactions leading to different indoles can be directed by changing the 2-alkynyl-phenylamine 1/alpha,beta-enone 3 ratio and the reaction temperature. Unusual gold-catalyzed rearrangement reaction of indoles are observed at 140 degrees C. New gold-catalyzed formation of propargyl-alkyl ether under mild conditions and the hydration reaction of N-acetyl-2-ethynyl-phenylamine are reported.     

Iminofuran chemistry: VII. Intramolecular cyclization of 2-N-aryl-substituted derivatives of 2-amino-4-aryl-4-oxobut-2-enoic and 2-amino-5,5-dimethyl4-oxohex-2-enoic acids

The cyclization at the treatment of acetic anhydride of 4-aryl-2-arylamino-4-oxobut-2-enoic and 2-arylamino-5,5-dimethyl-4-oxohex-2-enoic acids was investigated furnishing derivatives of 5-aryl-3-aryl-imino-3H-furan-2-ones and 4-arylamino-2-tert-butyl-2,5-dihydro-5-oxofuran-2-yl acetate respectively. 2-N²-Methylenesubstituted 4-aryl-2-hydrazino-4-oxobut-2-enoic and 5,5-dimethyl-2-hydrazino-4-oxohex-2-enoic acids cleanly underwent cyclization under the effect of acetic anhydride into 5-aryl-3-hydrazono-3H-furan-2-ones and 5-tert-butyl-3-hydrazono-3H-furan-2-ones.     

Gas-phase nazarov cyclization of protonated 2-methoxy and 2-hydroxychalcone: An example of intramolecular proton-transport catalysis

Upon CA, ESI generated [M + H]⁺ ions of chalcone (benzalacetophenone) and 3-phenyl-indanone both undergo losses of H₂O, CO, and the elements of benzene. CA of the [M + H]⁺ ions of 2-methoxy and 2-hydroxychalcone, however, prompts instead a dominant loss of ketene. In addition, CA of the [M + H]⁺ ions of 2-methoxy-β-methylchalcone produces an analogous loss of methylketene instead. Furthermore, the [M + D]⁺ ion of 2-methoxychalcone upon CA eliminates only unlabeled ketene, and the resultant product, the [M + D − ketene]⁺ ion, yields only the benzyl-d ₁ cation upon CA. We propose that the 2-methoxy and 2-hydroxy (ortho) substituents facilitate a Nazarov cyclization to the corresponding protonated 3-aryl-indanones by mediating a critical proton transfer. The resultant protonated indanones then undergo a second proton transport catalysis facilitated by the same ortho substituents producing intermediates that eliminate ketene to yield 2-methoxy- or 2-hydroxyphenyl-phenyl-methylcarbocations, respectively. The basicity of the ortho substituent is important; for example, replacement of the ortho function with a chloro substituent does not provide an efficient catalyst for the proton transports. The Nazarov cyclization must compete with an alternate cyclization, driven by the protonated carbonyl group of the chalcone that results in losses of H₂O and CO. The assisted proton transfer mediated by the ortho substituent shifts the competition in favor of the Nazarov cyclization. The proposed mechanisms for cyclization and fragmentation are supported by high-mass resolving power data, tandem mass spectra, deuterium labeling, and molecular orbital calculations.