Synthèse d'analogues azotés d'esters chrysanthémiques et pyréthriques

3,3-Dimethyl-2-vinyl-l-ethoxycarbonylaziridines were prepared from 2-acylaziridines and phosphoranes, phosphonate or silyl anions. A 3,3-di-methyl-2-ethoxycarbonyl N-vinylaziridine was also prepared. These compounds constitute some analogues of chrysanthemic and pyrethric acid esters.     

Synthesis and thermal transformations of spiro-fused N-phthalimidoaziridines

Oxidation of N-aminophthalimide in the presence of 2-arylideneinden-1,3-diones with electron-withdrawing substituents gives the corresponding 3-aryl-1-phthalimidospiro[aziridine-2,2′-indene]-1′,3′-diones in good yields. Heating these aziridines with standard dipolarophiles (N-phenylmaleimide, dimethyl acetylenedicarboxylate, maleate, and fumarate) leads, in most cases, to spiro[inden-2,2′-pyrrole] derivatives as products of 1,3-dipolar cycloaddition of the intermediate azomethine ylides with up to 70–95% yields in the case of N-phenylmaleimide. As is typical for 2-acylaziridines, the competing rearrangement into 2-aryl-4H-indeno[2,1-d][1,3]oxazol-4-ones prevails for less active dipolarophiles. Increasing the electron-releasing properties of the 3-aryl ring allows the observation of the push–pull effect of electron-donating and electron-withdrawing substituents on the ease of the three-membered ring-opening.     

Facile access to pyrazolines via domino reaction of the Huisgen zwitterions with aziridines

A novel, efficient, and general domino reaction of 2-acylaziridines with the Huisgen zwitterions to furnish 2-pyrazoline rings is described. A possible mechanism for the domino sequence is proposed.     

Dicobalt octacarbonyl promoted rearrangement of 4-isoxazolines to acylaziridines: dramatic rate acceleration with very high substrate tolerance

[reaction: see text] Dicobalt octacarbonyl [Co(2)(CO)(8)] in acetonitrile at 75 degrees C triggers the cleavage of the N-O bond of 4-isoxazolines (1) to bring about the valence rearrangement to 2-acylaziridines (2). The isoxazolines were stable at 75 degrees C in the absence of the cobalt complex.     

A Convenient Synthesis of N,N, N'-Trisubstituted Ethylenediamine Derivatives From 2-Methyl-2-imidazoline

A series of N, N, N'-trisubstituted ethylenediamine derivatives has been prepared from 2-methyl-2-imidazoline by a convenient three-step process in high yields: sulfonylation, methylation, and reactions with nucleophiles.     

Synthesis of 2,3-disubstituted benzo[b]furans by the palladium-catalyzed coupling of o-iodoanisoles and terminal alkynes, followed by electrophilic cyclization

[reaction: see text] 2,3-Disubstituted benzo[b]furans are readily prepared under very mild reaction conditions by the palladium/copper-catalyzed cross-coupling of various o-iodoanisoles and terminal alkynes, followed by electrophilic cyclization with I2, PhSeCl, or p-O2NC6H4SCl. Aryl- and vinylic-substituted alkynes undergo electrophilic cyclization in excellent yields. Biologically important furopyridines can be prepared by this approach in high yields.     

Preparation and addition--elimination reactions of benzyl alpha,beta,beta-trifluoroacrylate. A new stereoselective approach to (Z)-beta-substituted alpha,beta-difluoroacrylates

Benzyl alpha,beta,beta-trifluoroacrylate (1) was prepared in good yield via the reductive Br-F elimination of benzyl 2-bromo-2,3,3,3-tetrafluoropropanoate or the palladium-catalyzed cross-coupling reaction of 1,2,2-trifluorovinylstannane with benzyl chloroformate. On treating 1 with various Grignard reagents or dialkylzinc reagents in the presence of copper(I) salt, the corresponding beta-substituted alpha,beta-difluoroacrylates were obtained in high yields with high Z-selectivity. Additionally, trialkylaluminum reagents were also found to be good nucleophiles, the corresponding addition-elimination products being afforded in good yields but with low stereoselectivity.     

General, stereoselective synthesis of (Z)-beta,gamma-unsaturated nitriles promoted by samarium diiodide

A method to obtain (Z)-beta,gamma-unsaturated nitriles in high or good yields and with moderate or high stereoselectivity is described. The products were achieved through the photoinduced metalation of 3-acetoxy-4-chloronitriles with SmI2. The starting compounds were readily prepared, and a mechanism is proposed to explain this stereoselective beta-elimination reaction.     

Synthesis of 3-phenylpyrroles by hydride reduction of 4-hydroxypyrrolidin-2-ones

3-Phenylpyrroles 2 were easily prepared in good yields by hydride reduction of 4-hydroxypyrrolidin-2-ones 1 , which have been prepared in high yields from the photoreaction of N,N-dialkylbenzoylacetamides, with lithium aluminum hydride.     

Asymmetric Catalysis by Vitamin B12: The Isomerization of Achiral Aziridines to Optically Active Allylic Amines

Achiral N-acylaziridines are isomerized to optically active N-acyl-allylamines in ee's of up to 95% by catalytic amounts of cob(I)alamin in MeOH.     

Coupling reaction of zirconacyclopentadienes with dihalonaphthalenes and dihalopyridines: a new procedure for the preparation of substituted anthracenes, quinolines, and isoquinolines.

Reactions of tetraiodobenzene with zirconacyclopentadienes, which were conveniently prepared from two alkynes (or diynes) and zirconocene complexes, afforded 1,2,3,4-tetrasubstituted diiodonaphthalene derivatives in good isolated yields. These 1,2,3,4-tetrasubstituted diiodonaphthalene derivatives could be converted to 1,2,3,4,5,6,7,8-octasubstituted anthracene derivatives by reaction with a second zirconacyclopentadiene. When the two zirconacyclopentadienes were different, unsymmetrical anthracenes such as 1,2,3,4-tetraethyl-5,6,7,8-tetraphenylanthracene (68% isolated yield) were obtained. On the other hand, treatment of a 2,3-dihalopyridine such as 2-bromo-3-iodopyridine with zirconacyclopentadienes gave 5,6,7,8-tetrasubstituted quinoline derivatives in good to high yields. 3,4-dihalopyridines such as 4-chloro-3-iodopyridine reacted with zirconacyclopentadienes to afford 5,6,7,8-tetrasubstituted isoquinoline derivatives in good to high yields.     

One-step synthesis of some polyfluoroalkylated 1,3-benzodioxoles, 4H-l,3-benzodioxins anddibenzo[d,f] [l,3]dioxepins

Several polyfluoroalkylated heterocyclic compounds containing methylenedioxy group such as 2-(F-alkyl) substituted 1,3-benzodioxole, piperonal, 4H-1,3-benzodioxin, 1,3-dioxolane and 6-(F-alkyl) substituted dibenzo[d,f][1,3]dioxepin have been prepared through double Michael-addition reactions of 2,2-dihydropolyfluoroalkanoates with the corresponding diphenols or diols in high yields.     

An efficient reagent for the phosphorylation of deoxyribonucleosides, DNA oligonucleotides, and their thermolytic analogues

[reaction: see text] The phosphoramidite 11 was prepared in three steps from methyl 2-mercaptoacetate and demonstrated efficiency in the synthesis of conventional 5'-/3'-phosphate/thiophosphate monoester derivatives of 2'-deoxyribonucleosides and DNA oligonucleotides. Moreover, the use of 11 has enabled the preparation of the dinucleoside phosphorothioate analogue 26 in high yields (>95%) with minimal cleavage (<2%) of the thermolytic thiophosphate protecting group.     

Efficient and Green Preparation of 2-Amino-4H-chromenes by a Room-Temperature,Na2CO3-Catalyzed,Three-Component Reaction of Malononitrile,Benzaldehydes, and Phloroglucinol or Resorcinol in Aqueous Medium

The preparation of substituted 2-amino-4H-chromenes by a Na₂CO₃-catalyzed reaction of malononitrile, benzaldehydes, and phloroglucinol or resorcinol in aqueous medium and at room temperature is reported. The merits of this procedure include limited use of organic solvents, easy workup technique, and high purity of products. The 2-amino-4H-chromenes were prepared in yields of 54–96%.     

One-pot synthesis, photoluminescence, and electrocatalytic properties of subnanometer-sized copper clusters

Subnanometer-sized copper nanoclusters were prepared by a one-pot procedure based on wet chemical reduction. The structural characteristics of the 2-mercapto-5-n-propylpyrimidine-protected nanoclusters, Cu(n) (n ≤ 8), were determined by mass spectrometry. The Cu nanoclusters displayed apparent luminescence, with dual emissions at 425 and 593 nm, with quantum yields of 3.5 and 0.9%, respectively, and high electrocatalytic activity in the electoreduction of oxygen.     

新型手性N,P配体的合成及其在烯丙基化中的应用

以手性5,6,7,8-四氢-8-喹啉醇为原料合成了新型手性N,P配体, 并将该配体应用于钯催化的1,3-二苯基-2-烯丙基乙酸酯的不对称烯丙基化反应, 得到100%的取代产物, 对映体过量达到73% ee.     

One-step synthesis of some polyfluoroalkylated 1,3-benzodioxoles, 4H-1,3-benzodioxins and dibenzo[d,f] [1,3]dioxepins

Several polyfluoroalkylated heterocyclic compounds containing methylenedioxy group such as 2-(F-alkyl) substituted 1,3-benzodioxole, piperonal, 4H-1,3-benzodioxin, 1,3-dioxolane and 6-(F-alkyl) substituted dibenzo[d, f][1,3]dioxepin have been prepared through double Michael-addition reactions of 2,2-dihydropolyfluoroalkanoates with the corresponding diphenols or diols in high yields.     

The synthesis of pyrrole bis-coumarins, new structures for fluorescent probes

Pyrrole bis-coumarins as fluorescent probes have been synthesized from 1,4-dicoumarinyl-1,4-diones, themselves prepared in moderate to high yields in one step from the corresponding α-bromo-3-acetylcoumarins using Zn-I₂. The mechanism of the reaction can be explained through a Wurtz-like self-condensation of α-bromo-3-acetylcoumarins.     

A three-component,intramolecular Ugi reaction toward unique indoloketopiperazines

2-(3-Chloro-2-formyl-1H-indol-1-yl) acetic acid, as a bifunctional formyl-acid, is prepared in three steps. This compound undergoes a one-pot, four-center, three-component Ugi reaction with primary amines and alkyl isocyanides. A series of novel substituted indoloketopiperazine derivatives are obtained in moderate to high yields.     

3,3]-Sigmatropic rearrangement/5-exo-dig cyclization reactions of benzyl alkynyl ethers: synthesis of substituted 2-indanones and indenes

Substituted benzyl alkynyl ethers, prepared from the corresponding α-alkoxy ketones in a two-step sequence involving enol triflate formation and KOtBu-induced E2 elimination, undergo [3,3]-sigmatropic rearrangement/intramolecular 5-exo-dig cyclization at 60 °C to form substituted 2-indanones in good overall yields. 1,3-cis-Disubstituted-2-indanones are formed preferentially when the benzylic substituent R(1) is bulky. Substituted indenes may be prepared from 2-indanones in high yields by Horner-Wadsworth-Emmons reaction.