共查询到20条相似文献,搜索用时 15 毫秒
1.
Ivana Vinkovi? Vr?ek 《Tetrahedron letters》2004,45(4):699-702
An unexpected and previously unknown reaction sequence in the interactions of the acyl halides with nitrosobenzenes, which involves carbon-nitrogen bond formation followed by heterolytic nitrogen-chlorine bond cleavage giving the corresponding unsubstituted N-phenylalkylhydroxamic acids (or N-phenylarylhydroxamic acids) and chlorine as the products has been observed. The kinetic and other evidence obtained suggest that the carbon-nitrogen bond formation is the consequence of a nucleophilic interaction of an N-phenylchlorohydroxylamine intermediate, formed in the first reaction step, with the acyl halide in the second step of the complex sequence, which leads to an N-acyl-N-chlorophenylhydroxylamine cation intermediate. The key reaction step involves the interaction of an N-acyl-N-chlorophenylhydroxylamine cation intermediate with chloride ion, which leads to the N-Cl heterolytic bond cleavage and the final formation of the hydroxamic group and a molecule of chlorine. 相似文献
2.
Thermolysis of alk-1-enyl-N-phthalimidoaziridines leads to products of 1,5-electrocyclization of intermediate azomethine ylides with participation of C=C bonds. If acyl or alkoxycarbonyl substituent is present in the aziridine ring, the C=O bond is also involved. Thermolysis of the title compounds in the presence of N-phenylmaleimide or dimethyl acetylenedicarboxylate under analogous conditions gives products of 1,3-dipolar cycloaddition of azomethine ylides to the double or triple bond of the dipolarophile. 相似文献
3.
《Tetrahedron: Asymmetry》2000,11(16):3273-3276
An orthogonally protected 3-(1-aminoalkyl)isoxazole-4-carboxylic acid has been prepared by 1,3-dipolar cycloaddition of a suitably protected α-aminonitrile oxide with an enaminoester dipolarophile; this protected amino acid has been deprotected and coupled independently at either the C- or N-terminus to produce pseudopeptide segments as peptide mimetics that contain a cis-amide bond replacement. 相似文献
4.
Cristina M. Al Matarneh Catalina I. Ciobanu Mircea O. Apostu Ionel I. Mangalagiu Ramona Danac 《Comptes Rendus Chimie》2018,21(1):1-8
A comparative study regarding cycloaddition versus amidation reactions of 2-amino-2-oxoethyl-phenanthrolinium ylides to activated alkynes and alkenes is presented. The reaction pathway is different, depending on dipolarophile (with triple or double bond) and ylide structures. The monoenamidation reaction proved to be stereoselective leading to a Z-stereochemistry on the acrylate double bond. The structures of all newly synthesized compounds have been proved by spectral analysis (NMR and IR) and in some cases by X-ray diffraction. 相似文献
5.
Ujjal Kanti Roy 《Journal of organometallic chemistry》2006,691(8):1525-1530
A base free one-pot conversion of azides to N,N-dialkylamine is described. A two-step reaction pathway has been postulated invoking the intermediacy of stannaimine. This new carbon-nitrogen bond formation strategy adds to the repertoire of tin(II) chemistry. 相似文献
6.
The first synthesis of 1,3-oxaselenepane derivatives by the reaction of aryl isoselenocyanates with 4-bromobutanol in the presence of sodium hydride in THF as a one-pot reaction is described. The Z/E isomerism for the exocyclic carbon-nitrogen double bond in the selenium heterocycles was observed for the first time. 相似文献
7.
Thermally induced opening of the diaziridine ring in 6-aryl-2-methyl-1,5-diazabicyclo[3.1.0]-hexanes at the carbon-nitrogen bond is characterized by low regioselectivity; isomerization of unstable intermediate azomethine imines leads to mixtures of the corresponding 1-arylmethyl-5-methyl-4,5-dihydro-1H-pyrazoles and 1-arylmethyl-3-methyl-4,5-dihydro-1H-pyrazoles at a ratio of ~6:5. Analogous regioselectivity in opening of the three-membered ring is observed in the presence of phenyl isocyanate. In this case, adducts with cis arrangement of the aryl and methyl groups are formed as the major products (cis/trans ratio ~3:1). 相似文献
8.
A syn-anti photoisomerisation of the carbon-nitrogen double bond is responsible for the photochromic properties observed with 2-arylhydrazones of 2-substituted 1,2-diketones. We have determined the multiplicity of the excited state involved in the process and we have shown that, in the thermal back-reaction, syn-anti isomerisation takes place through rotation around the CN bond rather than through inversion of the nitrogen atom. 相似文献
9.
Miho Katoh 《Tetrahedron letters》2007,48(27):4691-4694
Enantioselective synthesis of (R)-deoxydysibetaine and (−)-4-epi-dysibetaine was achieved by employing a samarium iodide-promoted reductive carbon-nitrogen bond cleavage of a proline derivative, as a key reaction. 相似文献
10.
Miho Katoh 《Tetrahedron letters》2005,46(31):5161-5163
A stereoselective synthetic route to Nuphar quinolizidine alkaloid, (−)-deoxynupharidine, was established by employing reductive carbon-nitrogen bond cleavage, followed by simultaneous recyclization of a proline derivative with samarium diiodide, and an intramolecular ring-closing metathesis, as the key steps. 相似文献
11.
Miu Suen Lam 《Tetrahedron letters》2008,49(43):6192-6194
An efficient copper-catalyzed carbon-nitrogen bond formation is described. The copper(I) complex with commercially available 2-picolinic acid ligand was found to be effective in N-arylation of N-Boc-hydrazine. This methodology offers a regioselective N-arylation of hydrazides using a variety of substituted aryl iodides. 相似文献
12.
M. S. Novikov A. F. Khlebnikov M. A. Egarmin M. V. Shevchenko V. A. Khlebnikov R. R. Kostikov D. Vidovic 《Russian Journal of Organic Chemistry》2006,42(12):1800-1812
N-Substituted 9H-fluoren-9-imines react with difluorocarbene to give the corresponding iminium ylides whose further transformations in the absence of active dipolarophiles depend on the substituent at the nitrogen atom and reaction conditions. N-Ethyl-, N-benzyl-, and N-(2-phenylethyl)-9H-fluoren-9-imines are thus converted in low yield into the formal cyclodimerization products and/or 9H-fluorene-9-carboxamides. N-Methyl-substituted fluoreniminium ylide readily adds at the C=N bond of initial N-(9H-fluoren-9-ylidene)-methanamine with formation of spiro-fused imidazolidine derivative; in the presence of fluorenone, acetaldehyde, or benzaldehyde, addition at the C=O group of the dipolarophile occurs to give the corresponding oxazolidine derivatives. The regioselectivity of the cycloaddition of iminium ylides having a fluorene fragment at a double carbon-heteroelement bond can be described by quantum-chemical calculations in terms of the density functional theory (DFT; local hard and soft acids and bases concept): the cycloaddition leads preferentially to the 2,2-difluoro-substituted adduct. 相似文献
13.
Jayadevan Jayashankaran 《Tetrahedron letters》2004,45(39):7303-7305
A comparative study of the synthesis of novel dispiro pyrrolo/pyrrolizidino ring systems by the cycloaddition of azomethine ylides generated by a decarboxylative route from sarcosine/proline and isatin with the dipolarophile 9-arylidine-fluorene using four different methodologies is described. A solvent-free microwave-assisted approach gave products with the highest yields in a short time. Additionally, our solvent-free approach allowed the use of 4-N,N-dimethylaminobenzaldehyde, which failed to yield the desired cycloadducts under conventional approaches. 相似文献
14.
An efficient cascade approach to α-hydroxy-β-amino acid derivatives is reported, which goes through a 1,3-dipolar cycloaddition of carbonyl ylides and N-benzoylbenzyl imines and followed by hydrolysis under acidic conditions. This is the first example of using N-benzoylbenzyl imine as dipolarophile for 1,3-dipolar cycloaddition with carbonyl ylide, which provides a direct and convenient access for the one-pot synthesis of paclitaxel side chain and its derivatives. 相似文献
15.
Treatment of 2-phenyl-3-vinyl-substituted 2H-azirines with Grubbs' catalyst induces a clean rearrangement and affords products derived from carbon-nitrogen bond cleavage of the 2H-azirine ring. However, when the reaction was carried out using Wilkinson's catalyst in an alcoholic solvent, the only product obtained in high yield corresponded to an α,β-unsaturated oxime. 相似文献
16.
Efficient synthesis of tricyclic indole derivatives bearing a substituent at the 3-position of the indole nucleus was achieved by the [3+2] cycloaddition reaction of transition metal-containing azomethine ylides derived from N-(o-alkynylphenyl)imines with vinyl ethers. Third-row transition metal complexes, especially PtCl2, turned out to be highly efficient for the reaction of internal alkynes and imidate substrates with wide generality. Moreover, as strong support for the reaction mechanism, the intermediate Pt-carbene complex was found to undergo intramolecular C-H bond insertion reaction to give tetracyclic indoline derivatives when benzyl vinyl ether was employed as a dipolarophile. This protocol provided a facile synthesis of highly functionalized tricyclic indole derivatives found as the basic skeleton of the mitosene family, such as mitomycin C. 相似文献
17.
M. Vojtech 《Tetrahedron letters》2008,49(19):3112-3116
Treatment of the sodium nitronate forms of 1-deoxy-1-nitrohexitols with methanolic sulfuric or hydrochloric acid at −30 °C leads to their regiospecific conversion to the corresponding methyl glycofuranosides. The reaction exhibits more pronounced stereoselectivity for 1-deoxy-1-nitroalditols with the 2,3-erythro configuration than with the 2,3-threo substrates and cis methyl glycofuranosides are the major products. The observed stereoselectivity indicates the lysis of the protonated aci-nitro form which is a two-step process consisting of nucleophilic addition to the protonated carbon-nitrogen double bond followed by the bimolecular nucleophilic substitution of the nitrogen-containing residue. 相似文献
18.
The three-component condensation of dimedone, 2-naphthylamine, and formaldehyde in aliphatic alcohols under mild conditions gives in high yields the corresponding N-alkoxymethyl benzo[f]quinoline derivatives having a substituted 2-azaspiro[5.5]undecane fragment. The reaction involves formation of three new carbon-carbon bonds, two carbon-nitrogen bonds, and one carbon-oxygen bond, and the initial β-dicarbonyl system is conserved. 相似文献
19.
One-pot multistep reactions involving a new environmentally friendly catalytic procedure have been developed for the synthesis of benzimidazoles. Benzimidazole derivatives with biological and pharmaceutical interest have been prepared by a one-pot four step process with a solid catalyst containing basic and oxidation sites. The four steps refer to: (a) oxidation of the alcohol; (b) cyclocondensation of the aldehyde formed with ortho-phenylenediamines, (c) oxidation of the carbon-nitrogen bond, (d) N-alkylation reaction. The process is illustrated by the synthesis of 1,2-disubstituted benzimidazole derivative with antiviral activity. 相似文献
20.
Based on quantitative transformation of unsaturated polyesters into Δ2-pyrazoline polymers when reacted with 1,3-dipoles, attempts were made to apply the same reaction to unsaturated polyamides and polyhydrazides having double bonds conjugated with a carbonyl group. One could not obtain heterocyclic polymers because of factors discussed in the paper. The presence of an active hydrogen atom in the molecule of polyamide or polyhydrazide causes a decrease of the dipolarophile capacity of the double bond. Substitution of these hydrogen atoms, both in model compounds and polymers, leads to the expected results. Thus N-alkylpolyamide was quantitatively transformed into the Δ2-pyrazoline polyamide. 相似文献