Immobilization and reuse of Pd complexes in ionic liquid: efficient catalytic asymmetric fluorination and Michael reactions with beta-ketoesters

[reaction: see text] Palladium complexes (1 and 2) were immobilized in ionic liquids, and their applications to catalytic asymmetric fluorination and Michael reaction of beta-ketoesters were successfully demonstrated. This immobilization enabled the reuse of the catalysts no less than 10 times in fluorination and 5 times in Michael reaction with levels of efficiency comparable to those obtained in usual organic solvents.     

钯催化下三正丁基杂环基锡和酰氯及取代芳烃偶联反应的研究

本文研究了在Pd(PPh3)2Cl2(1)催化下的三正丁基-2-呋喃基锡(6a), 三正丁基-2-噻吩基锡(6a), 三正丁基-2-(N-甲基)吡咯基锡(6c)和菊酰氯(5), 肉桂酰氯(7)的交联反应。发现除了三正丁基-2-(N-甲基)吡咯与5的不寻常反应得到2, 5-二取代的吡咯衍生物外, 其余反应皆以70～87%的产率得到交叉偶联产物。本文同时还报道了钯催化下有机锡试剂与取代卤代芳烃反应, 高收率地得到了不对称的杂环基芳烃和双杂环化合物。在合成的交联产物中, 化合物2, 8, 9, 15, 16与17均为新化合物。     

Mild and Efficient Catalytic Protocol for Tetrahydropyranylation of Alcohols Using Acidic Keggin and Wells‐Dawson Structures

A simple, mild and effective procedure is reported to the generation of 2-tetrahydropyranyl acetals from alcohols. Keggin and Wells-Dawson heteropolyoxometalates were used as catalysts at ambient temperature in acetone as solvent with good yields and high selectivities in a short reaction time. Different reaction parameters affecting efficiency of the protocol were also studied. The use of these acid catalysts allows replacing the usual soluble inorganic acids, contributing to waste reduction.     

Diastereoselective synthesis of 2-fluoroaziridine-2-carboxylates by Reformatsky-type aza-Darzens reaction

The reaction of ethyl dibromofluoroacetate with imines using zinc metal gave 2-fluoroaziridine-2-carboxylates via aza-Darzens reaction of the primary product of the Reformatsky reaction with high diastereoselectivity in excellent yields (quantitative yield and Dr = 85:15). This chemoselective formation of 2-fluoroaziridines was achieved by using CH₃CN as a solvent. Interestingly, the reaction proceeded without activation of zinc metal, which was necessary for the Reformatsky reaction of bromodifluoroacetate. None of α-bromo-α-fluoro-β-lactams, four-membered cyclization products, and noncyclized 3-amino-2-bromo-2-fluorocarboxylic esters, usual Reformatsky adducts, were formed.     

Unusual regioselective mercuration of metalloporphyrins and its potential applications

The reaction of Hg(CF3CO2)2 with metalloporphyrins produces mercurated porphyrins regioselectively, the reaction, surprisingly occurring at the most hindered betaB-position; this behavior is in marked contrast to the usual electrophilic substitution reactions of porphyrins, whose reactions produce meso-substituted porphyrins; the obtained mercurated porphyrins are active to transition metal-catalyzed coupling reactions, such as the Mizoroki-Heck reaction.     

Simple, chemoselective, and diastereoselective Reformatsky-type synthesis of α-bromo-α-fluoro-β-lactams

The chemoselective and diastereoselective synthesis of syn-α-bromo-α-fluoro-β-lactams was achieved using the diethylzinc-mediated Reformatsky-type reaction of ethyl dibromofluoroacetate with imines. The reaction led to diastereomerically pure β-lactams in good to moderate yields (up to 78% yield) with only small amounts of aziridine derivatives. Noncyclized 3-amino-2-bromo-2-fluoro carboxylic esters, usual Reformatsky adducts, were not formed. In contrast, reactions carried out under typical Reformatsky conditions using zinc metal were poorly chemoselective, leading to mixtures of β-lactams and aziridine derivatives.     

Reaction of α-halo ketone with 2-aminothiol: a new synthesis of thiazolidines with the oxo group migrated to the original position occupied by halogen atom

The reaction of 2-bromo-3-oxo steroids with 2-aminoethanethiol led to the stereoselective formation of spiro[steroid-3,2′-thiazolidin]-2-ones as the major product. With both cyclic and acyclic α-halo alkanones, the reaction gave the thiazolidines with the oxo group migrated to the original position occupied by the halogen atom. In addition, it was found that the use of microwaves affords improvement of yields and shortening the reaction time in comparison with usual conditions.     

Synthesis of 2-propyloxazole and 2-propyloxazole-4-carboxylic acid derivatives

2-Propyloxazole (VI) was obtained in a number of steps starting from butyronit rile. The hydrazide and amide were obtained from ethyl 2-propyloxazole-4-carboxylate; the amide was converted to the nitrile, from which the thioamide and amidoxime were obtained by the usual method. Attempts to convert VI to 2-propylisonicotinic acid or its nitrile by the reaction of VI with acrylic acid or acrylonitrile did not give positive results.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 7–9, January, 1972.     

Harnessing the Lewis Acidity of HFIP through its Cooperation with a Calcium(II) Salt: Application to the Aza‐Piancatelli Reaction

A method to extend the scope of the aza‐Piancatelli reaction between 2‐furylcarbinols and anilines is depicted. We found that 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) is the solvent of choice for this transformation, as it outcompetes the usual solvents in terms of rate and yield. Side reactions and other issues raised by the title reaction are prevented, thereby providing an avenue to complex molecules that were previously inaccessible. Lewis acidity studies and computations were carried out to unveil the role of HFIP. Based on these results, we propose that HFIP is, in fact, acting as a Lewis acid and that its acidity can be enhanced when combined with a calcium(II) salt.     

Synthese de F-alkyl oxirannes

The perfluoroalkyloxirans were obtained with good yields from the long chain perfluoroalkyl ethylenes R_FCHCH₂. All the reaction intermediates were isolated and described. Their structure was determinated by the usual spectroscopy methods : N.M.R., infra-red, mass spectrometry and by microanalysis.     

Palladium catalyzed Heck reaction of arenediazonium tetrafluoroborate salts with Baylis-Hillman adducts: production of α-benzyl-β-keto esters

A novel experimental procedure to obtain α-benzyl-β-keto esters from the Heck reaction between arenediazonium tetrafluoroborate salts and Baylis-Hillman (BH) adducts in the presence of Pd(OAc)₂ as catalyst is described. The methodology is simple, straightforward and the use of arenediazonium salts as opposed to conventional arylhalides/triflates over the usual Heck reaction is highlighted.     

Stereoselection in the Betti reaction of valine methyl esters

The multi-component Betti reaction of 2-naphthol, benzaldehyde and (S)-amines, that usually provides highly valuable aminobenzylnaphthol bearing two stereogenic centers, yielded a completely racemic product, when (S)-valine methyl ester was employed as the amine in the usual reaction protocol. The cause of this drawback, that appears to be overlooked in the literature, was investigated. As a result, new reaction conditions were set up, that were able to yield the expected useful product, having two fully resolved stereogenic centers. Furthermore, when the effect of substituents on the phenyl ring was preliminarily studied, we found that 4-fluoro- and 4-chlorobenzaldeyde gave stereoisomerically pure compounds also in the original reaction protocol.     

Research on the chemistry of phenoxazines

A third reaction center in the phenoxazinone molecule, viz., the 9 position in the benzenoid ring, was observed for the first time in the reaction of 3-phenoxazinone and its 2-hydroxy and 2-ethoxy derivatives with p-thiocresol. In conformity with this, 2,7,9-triarylthio derivatives are formed along with the usual 2,7-disubstituted derivatives of 3-phenoxazinone. The structures of the compounds obtained were confirmed by the PMR and EPR spectra and a number of chemical transformations.See [1] for Communication 11.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 40–44, January, 1980.     

Sur la ribosylation de divers mercapto-2 benzoazoles

A comparative study of the ribosylation reaction of various 2-mercaptobenzazoles using the three more usual techniques was performed: acid-catalyzed fusion, reaction of the silylated aglycones with 1-acetoxy and 1-halogeno sugars, respectively. For all the various 2-mercaptobenzazoles the N-nucleosides were obtained and fully characterized. The reactivity of 2-mercapto-benzimidazole is quite particular as we have noticed the formation of the corresponding N₁, N₃-diriboside and of an unusual 2-2-anhydro nueleoside.     

A novel reaction of dimethylsulfonium methylide with Michael acceptors: application to the synthesis of difficultly accessible vinyl silanes and styrenes

Rather than the usual cyclopropanation and Peterson-type olefination, conditions for a novel elimination reaction from the adduct of dimethylsulfonium methylide and 2-silylalkylidene/arylidene malonate/cyanoacetate/phosphonoacetate leading to geminally substituted vinyl silanes or styrenes, respectively, have been established.     

Polyhalogenated α-oxides—V : Role of steric factors in reactivity of polyfluorinated α-oxides

Steric shielding of the α-oxide 2-C-atom, as well as increase in the volume of the attacking nucleophilic agent, is shown to hinder the usual opening of polyfluorinated α-oxides at the 2-C-atom and to direct the nucleophilic attack to an other reaction centre. A mechanism of isomerisation of polyfluorinated α-oxides under the action of nucleophilic agents is suggested.     

Methoxide ion mediated reactions of methyl azidoacetate with 4-and 2-cyanobenzaldehyde. An unexpected cyclization of the ortho isomer to a 2(1H)-benzazepine derivative

A condensation reaction of 4-cyanobenzaldehyde ( 1 ) with methyl azidoacetate ( 2 ) in the presence of sodium methoxide produces a mixture of geometrical isomers of azidocinnamates 3 which undergoes thermolysis to give an indole 4 . By contrast, the treatment of 2-cyanobenzaldehyde ( 5 ) with 2 in the presence of sodium methoxide and followed by the usual workup furnishes an azepine derivative 6 .     

Unusual reductive behaviour of a trans-NiI2(RNC)2 complex at mercury and platinum electrodes

Electrochemical reactions of NiI₂(RNC)₂ (R = 2,6-Me₂C₆H₃) differed according to electrode materials. At a platinum electrode the reaction was shown by cyclic voltammogram to proceed in the usual electrochemical manner, but at a mercury electrode, there operated a CE mechanism.     

Synthesis of 3,4-Disubstituted Phosphorus-containing Furans with Free 2 and 5 Positions

A synthetic approach to -(chloromethyl)furans with free 2, 5 positions is developed. It isshown that these compounds enter the Michaelis-Becker reaction to form usual phosphorylation products.With 3,4-bis(diethoxyphosphorylmethyl)furan, two conformers with different chemical shifts of phosphorus nuclei and PCH₂ protons were detected.