Reactions of aminoguanidine with α-dicarbonyl compounds studied by electrospray ionization mass spectrometry

Aminoguanidine possesses extensive pharmacological properties. This drug is recognized as a powerful α-dicarbonyl scavenger. In order to better elucidate the reactivity of aminoguanidine with α-dicarbonyls, aminoguanidine was reacted with several aldehydic and diketonic α-dicarbonyls. Electrospray ionization mass spectrometry is a suitable technique to study chemical and biochemical processes, and was selected for the purpose. In aminoguanidine reactions, triazines were detected and, other compounds that have never been reported before were identified. Triazine precursor forms were detected, namely tetrahydrotriazines and singly dehydrated tetrahydrotriazines. Moreover, species with bicyclic ring structures, and dehydrated forms, were also identified in aminoguanidine reactions. These species appear to result from tetrahydrotriazines and triazines reactions with one dicarbonyl molecule. Experiments revealed that these bicyclic species, in particular the ones resulting from triazines reactivity, could exist in solution, since they were both identified in the reactions of aminoguanidine and of a selected triazine with the dicarbonyls studied. The results obtained, regarding aminoguanidine/triazines reactivities, appear to support the capability of triazines to condensate and form polycyclic ring structures, and also to support literature mechanistic data for dihydroimidazotriazines formation via dihydroxyimidazolidine-triazines. The data obtained in this study may prove to be valuable to complement solution information, concerning the reactivity of amines with α-dicarbonyls, in particular.     

A facile transformation of alkynes into α-amino ketones by an N-bromosuccinimide-mediated one-pot strategy

A facile efficient transformation of commercially available alkynes into α-amino ketones by an N-bromosuccinimidemediated one-pot cascade strategy was developed. A variety of α-amino ketones were obtained in moderate to good yields under mild conditions.     

Selective reduction of the acyl group in cyclic α-acyl-β-dicarbonyl compounds with sodium cyanoborohydride. Efficient synthesis of cyclic α-alkyl-β-dicarbonyl compounds

Efficient synthesis of cyclic -alkyl--dicarbonyl compounds of the cyclopentane, cyclohexane, tetronic acid, and -pyrone series from the corresponding cyclic -acyl--dicarbonyl compounds under the action of NaBH₃(CN) in a THF--HCl system is described.     

A new synthesis of alkynyl tellurides promoted by CsOH and 4(A°) MS

The mixture of cesium hydroxide and terminal alkynes in dry DMF in the presence of 4(A°), molecular sieves was stirred for 3.0 h at room temperature under N2, then aryltellurenyl bromide in THF was added, and the reaction mixture was stirred for 2.0 h. Alkynyl tellurides were obtained in about 90% yields by flash chromatography.     

A facile synthesis of α-aminophosphonates catalyzed by ytterbium perfluorooctanoate under solvent-free conditions

Three-component reactions of aldehydes, amines and diethyl phosphite are efficiently catalyzed by ytterbium perfluorooctanoate [Yb(PFO)₃] under solvent-free conditions, giving the corresponding α-aminophosphonates in good to excellent yields. The catalyst can be recovered and reused for several times without any significant loss of activity. Furthermore, a possible mechanism for this transformation is also presented.     

IBX/I2-mediated oxidation of alkenes and alkynes in water: a facile synthesis of α-iodoketones

The conversion of alkenes into α-iodoketones has been achieved in good yields and with high regioselectivity by means of iodohydrin formation and subsequent oxidation with 2-iodoxybenzoic acid (IBX) under mild conditions. Aromatic alkynes are also converted into their corresponding α-iodoketones under similar conditions.     

A facile synthesis of per (poly )fluoroalkyl substituted α-amino acid derivatives

Initiated by CrCl3/Fe redox couple, per(poly)fluoroalkyl iodides added to methyl a-acetylamino acrylate, giving B-per(poly)fluoroalkyl a-amino acid derivatives in good yields.     

A facile synthesis of bicyclic α-methylene-γ-lactones by intramolecular cyclization of allylsilylated aldehydes

Bicyclic α-methylene-γ-lactones were synthesized employing intramolecular reaction of an aldehyde unit with a β-ethoxycarbonylallylsilane function by the action of TiCl₄ in an excellent yield.     

Improved facile synthesis of α-amino phosphonates by the reaction of α-amido sulfones with dialkyl trimethyl silyl phosphites catalyzed by Fe(III) chloride

An improved efficient synthesis of α-amino phosphonates has been discovered by the reaction of N-benzyloxycarbonylamino sulfones with dialkyl trimethyl silyl phosphites in the presence of FeCl₃ as a catalyst. The products were formed in high yields (86–94%) within 2–4?h. The catalyst is inexpensive, easily available, and highly active. The unreacted dialkyl trimetyl silyl phosphites can easily be removed from the products due to their low boiling points. The sulfones can conveniently be prepared and are generally stable.     

Lead(IV) acetate mediated cleavage of β-hydroxy ethers: enantioselective synthesis of α-acetoxy carbonyl compounds

α-Acetoxy aldehydes or α-acetoxy ketones can be efficiently synthesized by treating 2,3-epoxy primary alcohols with lead tetraacetate. The reaction, which proceeds with complete regio- and stereoselectivity facilitates the enantioselective synthesis of α-acetoxy carbonyl compounds from allyl alcohols, via Sharpless epoxidation. Cyclic β-hydroxy ethers, with an oxygenated five-, six- or seven-membered ring, are transformed into α-acetoxy ethers.     

Novel Reaction of the [HFe3(CO)11]− reagent with alkynes: A new synthesis of cyclobutenediones

Reaction of the [HFe₃(CO)₁₁]⁻ species generated in situ using Fe(CO)₅ and NaBH₄/CH₃COOH in THF with alkynes, followed by CuCl₂.2H₂O oxidation leads to the corresponding cyclobutenediones in 60–73% yields.     

Synthesis of fullerene Γ-lactones by free radical reaction of C60 with ketones promoted by compounds of transition metals Cr(VI), Ce(IV)

One-step synthesis was developed for fullerene Γ-lactones by the reaction of C₆₀ with aromatic and aliphatic ketones in the presence of transition metal compounds CrO₃, K₂Cr₂O₇, (NH₄)₂Ce(NO₃)₆ ·6H₂O.     

Deoxygenation of some α-dicarbonyl compounds by tris(diethylamino)phosphine in the presence of fullerene C60

The reactions of such cyclic α-diketones as acenaphthenequinone, aceanthrenequinone, and N-alkylisatins, with hexaethyltriaminophosphine in the presence of the fullerene C(60), lead to the formation of methanofullerene derivatives under mild conditions. This process proceeds via deoxygenation of the dicarbonyl compound by the P(III) derivative and is likely to involve the intermediate formation of α-ketocarbenes. The structure of some methanofullerenes has been confirmed by NMR and XRD. The electrochemical behavior of the methanofullerenes was also investigated.     

Asymmetric synthesis of α-alkyl α-selenocarbonyl compounds catalyzed by bifunctional organocatalysts

A new organocatalytic approach for the synthesis of a variety of α-alkyl, α-phenylselenyl ketones as well as their corresponding esters and amides, by the addition of α-selenocarbonyl derivatives to nitroalkenes catalyzed by thiourea or squaramide cinchona catalysts, is presented. This catalytic system allows the preparation in high yields of enantiomerically enriched selenocarbonyl derivatives bearing two chiral centers with excellent ee's and dr's by using catalytic loadings of 3 mol%.     

A facile synthesis of α,α′-bis(substituted benzylidene) cycloalkanones catalyzed by p-TSA under solvent-free conditions

Abstract

Various 2,6-dibenzylidene cycloalkanones were readily prepared in a few minutes with good yields by simply mixing aromatic aldehydes with cycloalkanones in the presence of catalytic amounts of p-toluenesulfonic acid as a solid heterogeneous catalyst under solvent-free condition.     

Hypervalent iodine (III)-mediated oxidation of aryl sulfonylhydrazones: A facile synthesis of N-aroyl-N′-acyl arylsulfonylhydrazides

We have developed a novel and efficient method for the oxidation of aryl sulfonylhydrazones to N-aroyl-N′-acyl arylsulfonylhydrazides, using hypervalent iodine (III) reagent in good yields at room temperature.     

A facile synthesis of (R)-(−)-hexahydromandelic acid with fermenting baker's yeast

Optically pure (R)-(−)-hexahydromandelic acid has been prepared stereoselectively in two steps by the asymmetric reduction of ethyl α,2-dioxocyclohexaneacetate with fermenting baker's yeast followed by Clemmensen reduction.     

A new pyridine synthesis starting from α, β-unsaturated carbonyl compounds

A new and mild synthetic method of substituted pyridines from α, β-unsaturated carbonyl compounds through a sequence involing (1) 1, 4-conjugate addition of thiophenol (2) condensation with a methylene ketone (3) Pummerer rearrangement to an unsaturated 1, 5-dicarbonyl compound (4) treatment with ammonia is described.     

Reactions of (arene)tricarbonylchromium stabilized carbocations with aromatics and β-dicarbonyl compounds

Primary and secondary benzylic carbocations, stabilized by a tricarbonyl-chromium group, gave coupling products with several aromatics or β-dicarbonyl compounds in good yield and this reaction presents a new synthetic method for carbon-carbon bond formation. The chromium complexes of tertiary benzyl alcohols gave dehydrated products without carbon-carbon coupling products under similar conditions.