Acyloxy derivatives of trivalent phosphorus in amidoalkylation of hydrophosphoryl compounds

In order to model the previously suggested mechanism of the P-C bond formation via the Arbuzov reaction, we have studied the interaction of diethylacylphosphite (prepared beforehand as well as generated in situ from tetraethylpyrophosphite) with the in situ generated acyliminium cation. Various conditions of in situ generation of acylphosphite derivatives of P(III) from hydrophosphoryl compounds and acyliminium ions from N,N′-alkylidenebiscarbamates have been investigated: solvent nature, acid catalyst, and the reagents mixing order). The results obtained have confirmed the suggested mechanism of three-component reaction of amidoalkylation of hydrophosphoryl compounds with the formation of P-C bond via the Arbuzov reaction of in situ formed intermediates.     

孤岛渣油超临界水-合成气中悬浮床加氢裂化反应研究 Ⅱ. 不同氢源下的加氢裂化反应

为了研究替代氢源加氢的有效性,对孤岛渣油以磷钼酸为催化剂,在不同氢源(CO+H2/H2O、CO/H2O、H2/H2O、H2)中悬浮床加氢裂化反应进行了研究。结果表明,超临界水中现场发生的水-气转化反应提供的加氢氢源是一种具有高加氢活性的原子态氢。在适宜的反应条件下,孤岛渣油在超临界水-合成气中的加氢裂化反应过程在抑制生焦、反应产物分布等方面与对应的分子氢存在下孤岛渣油加氢裂化反应结果几乎一致,反应体系中水的存在主要作用是提供水-气转化反应的条件,在没有水-气转化发生的体系中,水的存在对加氢过程有抑制作用,总之、利用现场发生水-气转化反应为加氢提供氢源的孤岛渣油超临界水-合成气中悬浮床催化加氢裂化是一项有效的渣油加氢改质技术。     

Facile synthesis of 2-azaazulenes from thiobenzoyl isocyanates using trimethylsilyldiazomethane

The reaction of trimethylsilyldiazomethane with thiobenzoyl isocyanates, in situ generated from thiazole-4,5-diones, yielded diazoketones, which were converted into 2-azaazulenes by the intramolecular Buchner reaction.     

A Comparative Study of the Modification of Gold and Glassy Carbon Surfaces with Mixed Layers of In Situ Generated Aryl Diazonium Compounds

In situ generated aryl diazonium cations were synthesized in the electrochemical cell by reaction of the corresponding amines with NaNO₂ in aqueous HCl. This paper reports a study of the formation of mixed layers from in situ generated aryl diazonium cations. Firstly, glassy carbon (GC) and gold electrode surfaces were modified with five single in situ generated aryl diazonium salts to obtain their corresponding reductive potential followed by the modification of GC and gold surfaces with eight binary mixed layers of in situ generated aryl diazonium salts. The difference between GC and gold surfaces in terms of in situ formation of two‐component aryl diazonium salt films was compared. The behavior of the mixed layers formed from in situ generated aryl diazonium salts relative to diazonium salts that were pre‐synthesized prior to surface modification was also investigated. Cyclic voltammetry and X‐ray photoelectron spectroscopy were used to characterize the resulting modified GC and gold surfaces. It is found that for some aryl diazonium salts the potential at which reductive adsorption is achieved on gold and GC surfaces is significantly different. For the eight sets of binary mixed layers, the species with more anodic potential are more difficult to attach to the both GC and gold surfaces. The behavior of the mixed layers formed from in situ generated aryl diazonium salts and the pre‐synthesized diazonium salts is similar; which emphasizes the advantage of the in situ approach without any apparent difference in behavior to the presynthesized diazonium salts.     

Bifunctionalized Allenes,VII: Two Methods for One‐Pot Synthesis of Sulfonyl‐Functionalized Allenecarboxylates and Phosphorylated Allenes

Two new approaches to the synthesis of sulfonyl‐functionalized allenecarboxylates and phosphorylated allenes are described. 2‐Sulfonyl‐alka‐2,3‐dienoates were readily prepared in an one‐pot reaction by [2,3]‐sigmatropic rearrangement of sulfinato‐substituted 2‐alkynoates, in situ generated from ethyl propynoate and subsequent treatment with lithium diisopropyl (LDA), ketone, trimethylchlorosilane (TMSCl), and the corresponding sulfinyl chlorides. Preparation of 1‐sulfonyl‐alka‐1,2‐dienephosphonates and ‐1,2‐dienyl phosphine oxides consists of the reaction of the lithio compounds, in situ generated from phosphorylated allenes and LDA, with the corresponding sulfonyl chlorides.     

TiCl3/PhN2-mediated radical addition of ethers to aldimines generated in situ under aqueous conditions

Ti(III)-mediated one-electron reduction of phenyldiazonium cation, followed by phenyl radical α-H atom abstraction from ethers, leads to one-pot radical addition of ethers to the C-atom of imines generated in situ from the corresponding aldehydes and imines under aqueous conditions. The reaction is not limited to aromatic aldehydes and may be applied to imines generated in situ from formaldehyde and enolizable aldehydes.     

Hypervalent iodine(III) reagents as safe alternatives to alpha-nitro-alpha-diazocarbonyls

A cyclopropanation reaction involving iodonium ylides generated in situ allows for efficient preparation of substituted 1-nitro-1-carbonyl cyclopropanes. This robust cyclopropanation reaction can be performed in organic solvents, biphasic aqueous media, or under solvent-free conditions with alkene substrates. The iodonium ylides generated in situ display some surprising differences in reactivity when compared to alpha-nitro-alpha-diazocarbonyl compounds. They do not undergo O-H insertion reactions and exhibit reduced reactivity with certain alkenes. [reaction: see text]     

One-pot synthetic route to homoallylketones via selective combination of alkyne,ethylene and aldehyde mediated by AlCl3 and zirconocene

Zirconacyclopentenes generated in situ from alkynes and ethylene undergo selective reaction with aldehydes to afford homoallylketones in yields exceeding 70% in the presence of AlCl3.     

1,3-Dipolar cycloaddition reaction of two different azomethine ylides to C70

1,3-Dipolar cycloaddition to Cyo of an azomethine ylide,which was generated in situ from refluxing a mixture of cyclohexanone and DL-valine in chlorobenzene under N2 afforded a monoadduct and a bisadduct.Even for longer reaction time,however,only monoadduct was obtained from the reaction of C70 with an azomethine ylide generated from refluxing a mixture of 2-undecanone and 2-aminoisobutyric acid in chlorobenzene under N2 The electrochemical properties of all the products were studied by cyclic voltammetry.     

Multicomponent reactions involving zwitterionic intermediates for the construction of heterocyclic systems: one pot synthesis of aminofurans and iminolactones

The reaction of 1:1 zwitterionic intermediate generated in situ from dimethyl acetylenedicarboxylate (DMAD) and cyclohexyl isocyanide with aldehydes and quinones is described. The reaction of stoichiometric amounts of DMAD, isocyanide and aldehydes afforded 2-aminofurans in good yields, while the reaction with quinones gave iminolactones.     

Novel C-C bond formation through addition of ammonium ylides to arylaldehydes: a facile approach to beta-aryl-beta-hydroxy alpha-amino acid frameworks

Ammonium ylides generated in situ from [small alpha]-diazo esters and amines in the presence of catalytic Rh2(OAc)4, undergo an aldol-type reaction with aldehydes affording highly substituted amino acid frameworks in a convergent, three-component reaction.     

A facile reaction of imines with telluronium allylide. Highly stereoselective synthesis of vinylaziridines

The reaction of telluronium allylides with alkylimines, generated in situ from alpha-amidoalkyl sulfones, affords cis-alkylvinylarizidines with good stereoselectivity in good yields. However, the same ylides react with N-aryl imines to provide trans-vinylaziridines.     

Syntheses of 7-fluoro- and 6,7-difluoroserotonin and 7-fluoro- and 6,7-difluoromelatonin

The Abramovitch adaption of the Fischer indole synthesis gave low yields of 7-fluoro-5-methoxytryptamine due in part to decomposition during the required decarboxylation step. Therefore, 7-fluoro- and 6,7-difluoro-5-methoxytryptamines were prepared by reaction of aminobutyraldehyde (generated in situ from the diethyl acetal) with 2-fluoro- and 2,3-difluoro-4-methoxyphenylhydrazine, and the products converted to the corresponding serotonins. The melatonins were prepared by a one-pot reaction that involved in situ acetylation of the aminobutyraldehyde.     

Convenient, in situ generation of anhydrous hydrogen iodide for the preparation of alpha-glycosyl iodides and vicinal iodohydrins and for the catalysis of Ferrier glycosylation

[reaction: see text] Anhydrous hydrogen iodide is generated in situ by the reaction of solid iodine and a thiol. The HI thus generated has been employed for the efficient preparation of alpha-glycosyl iodides and vicinal iodohydrins from the corresponding glycosyl acetates and epoxides, respectively, and for Ferrier glycosylation of alcohols and thiols.     

Aglycon switch approach toward unnatural glycosides from natural glycoside with glycosyltransferase VinC

New aglycon switch approach using glycosyltransferase VinC was explored to create unnatural glycosides from natural glycoside in one-pot reaction. This aglycon switch comprises from two reactions, where NDP-vicenisamine generated in situ from natural glycoside vicenistatin and NDP by the reverse reaction is transferred to the targeted additional aglycons to form unnatural vicenisaminides by the forward reaction.     

Facile construction of three-membered rings via benzyne-promoted Darzens-type reaction of tertiary amines

A range of tertiary amines having electron-withdrawing groups were activated in situ by benzyne, generated from 2-(trimethylsilyl)phenyl triflate and a fluoride source, and participated in the Darzens-type reaction with carbonyl compounds, imines, and vinyl ketones to afford structurally diverse epoxides, aziridines, and cyclopropanes, respectively, in moderate to excellent yields with high trans-selectivity. The reaction involves in situ formation of unstrained ammonium ylides from tertiary amines and benzyne, proceeds in the absence of transition metals and strong bases, and tolerates a wide variety of functional groups.     

Fluoroaziridines as novel substrates in the modified Petasis reaction: synthesis of monofluorinated propargyl amines

Reaction of 2-fluoroaziridines with potassium alkynyltrifluoroborates in the presence of BF₃·OEt₂ leads to fluorinated propargyl amines in moderate to good yields. The reaction proceeds as an in situ isomerization of 2-fluoroaziridines to α-fluorinated imines, followed by the reaction of the imine with alkynyldifluoroborane, which is generated in situ from the potassium alkynyltrifluoroborates and BF₃·OEt₂.     

Synthetic studies on (-)-FR182877: construction of the ABCD ring system via the intramolecular cycloadditions (1)

Construction of the ABCD ring system of (-)-FR182877 via the highly diastereoselective intramolecular Diels-Alder (IMDA) reaction is described. The IMDA reaction of the α,β-unsaturated aldehyde generated in situ from the corresponding acetal successfully provided the desired product 14 possessing the AB ring system as the single diastereomer. The CD ring system was constructed by the subsequent IMHDA reaction and the additional experiment suggested that the diastereoselectivity of the IMHDA reaction could be related to the E/Z geometry of alkene 17, which was generated in situ from 16.     

Addition reactions of iodomethyllithium to imines. A direct and efficient synthesis of aziridines and enantiopure amino aziridines

An efficient and general synthesis of aziridines by the reaction of imines derived from p-toluenesulfonamides with in situ generated iodomethyllithium, with a simple and rapid experimental protocol, is reported for the first time. The reaction with the chiral aldimine derived from phenylalaninal allowed access to (2R,1'S)-2-(1'-aminoalkyl)aziridine with very high diastereoselectivity, in enantiopure form. A mechanism to explain this novel reaction is proposed.     

Titanocene-catalyzed regioselective syn-hydrosilation of alkynes

[reaction: see text] The titanium catalyst, which was generated in situ from titanocene dichloride and 2 equiv of butyllithium, was found to catalyze hydrosilation of a variety of alkynes with excellent regio- and syn-selectivity.