Réaction du n-bromosuccinimide sur les aryl-2 dioxolannes-1,3 d'eroulement de la réaction

Reaction of NBS with 1,3-dioxolanes fused to a bicyclo[2.2.1] skeleton involves two intermediates, the dioxolanylium ion and the 2-succinimido-1,3-dioxolane. Evidence is presented that the unusual stability of the former ionic species is due to the steric hindrance towards endo attack by bromide ion, thus leading to the succinimido compound which by action of hydrobromic acid formed insitu, yields the former ionic species which finally gives the dioxolane ring-opening products. Some factors influencing the efficiency of the NBS reaction with hindered dioxolanes are pointed out.     

Rh-catalyzed formation of dioxolanes from alpha-alkyl diazoesters: diastereoselective cycloadditions of carbonyl ylides with selectivity over beta-hydride elimination

Described here is a diastereoselective Rh-catalyzed method for the preparation of dioxolanes from alpha-alkyl-alpha-diazoesters. This represents the first general method for generating carbonyl ylides from alpha-diazoesters that possess beta-hydrogens, as such diazo compounds typically give rise to alkenes via beta-hydride elimination. Subsequent cycloaddition with aromatic aldehydes gives tetrasubstituted dioxolanes with unusually high diastereoselectivity. A model is set forth to explain the diastereoselectivity of the cycloaddition.     

Resolution and determination of the absolute configuration of 3,3′,4,4′-tetramethyl-1,1′-diphosphaferrocene-2-carboxaldehyde

Racemic 3,3′,4,4′-tetramethyl-1,1′-diphosphaferrocene-2-carboxaldehyde 1 was resolved via the formation of diastereomeric dioxolanes with (S)-(+)-1-phenyl-1,2-ethanediol. Four stereoisomers were separated by column chromatography. The absolute configuration of one of them (2′′R, 4′′S,1R) was established by X-ray diffraction. Acid hydrolysis of the dioxolanes afforded quantitatively (R)- and (S)-enantiomers of 1. Optical rotatory dispersion (ORD) spectra of both enantiomers are also reported.     

1H NMR spectra,configuration, and conformations of 2-mono- and 2,4-disubstituted 1,3-dioxolanes

The stereochemistry of 2-furyl-substituted 1,3-dioxolanes was studied. The ethane fragment of 2-monosubstituted dioxolanes displays the spectrum that is typical for an AA'BB' spin system, while the spectra of the 2,4-disubstituted compounds are typical for an ABC system. The contribution of the various conformational forms to the pseudorotation cycle of the dioxolanes is discussed on the basis of an analysis of the spectra by means of an iteration program.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No, 12, pp. 1613–1617, December, 1980     

Two carbon homologated alpha,beta-unsaturated aldehydes from alcohols using the in situ oxidation-Wittig reaction

The in situ oxidation-Wittig reaction, followed by subsequent hydrolysis, has been applied to the conversion of primary alcohols into alpha,beta-unsaturated aldehydes. This conversion, which proceeds via the intermediacy of the homologated unsaturated dioxolanes, gives good to excellent yields with a range of benzylic alcohols and heterocyclic methanols.     

Synthesis and Enantiomeric Selectivity of Chiral Crown Ethers

Condensation of (4S,5S)-4,5-dihydroxymethyl-2-substituted dioxolanes with polyethylene glycols ditosylates yielded new chiral crown ethers. By potentiometry the enantioselectivity of complexing between the compounds obtained and L- and D-valine methyl ester hydrochlorides was evaluated.     

Ylures de carbonyle dérivés de gem-dicyanoépoxydes : Stéréochimie des dioxolannes obtenus par addition d'aldéhydes aux ylures de carbonyle

The reaction of aldehydes with 1,1-dicyano oxirans gives dioxolanes. The structure of these adducts, established by NMR and through boron trifluoride equilibration, is proof of the CC ring scission of the oxirans. The effect of substituants on the reactivity of aldehydes with carbonyl ylides is discussed. The occurrence of a non concerted reaction is considered in an extreme case.     

[4+3] Cycloadditions of some allylic dioxolanes

Four allylic dioxolanes were prepared and reacted with several dienes in the presence of Lewis acids, affording [4+3] cycloadducts. The reaction could be conducted with catalytic amounts of Lewis acid. The use of a chiral Lewis acid gave a cycloadduct with only a low enantiomeric excess.     

Thiophene aldehyde and its derivatives. II

Condensation of thiophene-2-aldehyde with p-aminobenzoic and barbituric acids gives 2-thenylidene -p-aminobenzoic acid and 2-thenyl-idenebarbituric acid. Similarly, 5-nitro-thiophene-2-aldehyde gives 5-nitro-2-thenylidene-p-aminobenzoic acid and 5-nitro-2-thenyl-idenebarbituric acid. Condensation of thiophene-2-aldehyde with nitroethane gives 1-(2-thienyl)-2-nitroprop-1-ene; and 1-nitro-2-(2-thienyl-5-nitro) ethene is synthesized by nitrating thienylnitroethylene.     

Halogenocycloprop anation des dioxolannes ethyleniques et des enones correspondantes par les monohalogenocarbenoides

The monohalocyclopropanation of conjugated enones and their dioxolanes has been achieved by monohalocarbenoîds generated from methylene chloride and gem-dichloroethane. In both cases, besides expected chloro-adducts, corresponding bromo-adducts are obtained. Formation of these adducts involves halogen exchange by the primary chlorocarbenoid with lithium bromide associated with methyllithium. Conjugated enones give trans α-halocyclopropanic alcohols stereospecifically while unsaturated dioxolanes lead to cis and trans α-halocyclopropyl ketones with, generally, trans prédominating. The determination of configuration has been achieved by spectroscopic methods specially the LIS effect in NMR. Stereoselectivity effect of temperature and nature of the methyllithium reagent, are studied and discussed.     

Synthesis of New Chiral and Racemic 1,3‐Dioxolanes

A series of chiral 1,3‐dioxolanes, 3 – 12 , with >99% ee values, have been synthesized. This is the first study of chiral ketalization reaction starting from ketones with aryl, monosubstituted aryl, and long alkyl chains (C₁₁—AC₁₃). Their ee values were determined by chiral high‐performance liquid chromatography (HPLC) on Chiralcel OD column, using their racemic 1,3‐dioxolanes rac‐ 3 – 12 , which were also synthesized for the first time. These chiral and racemic 1,3‐dioxolanes were characterizated by infrared, NMR (¹H, ¹³C), mass spectrometry, elemental analysis, optical rotation, and chiral HPLC.     

Reaction of 2-aminothiophenol with acrylic acid and conversion of the resultant adducts

The reaction of acrylic acid with 2-aminothiophenol gives 5-carboxyethyl-2,3-dihydro-5H-benzo[b][1,4]-thiazepin-4-one and N-[2-(carboxyethylthio)phenyl]-α-alanine, while the reaction of acrylic acid with bis(2-aminophenyl) disulfide gives bis[2-(carboxyethylamino)phenyl] disulfide. The action of potassium thiocyanate in acid medium on the carboxyethylamino derivatives yields 1-[2-carboxyethylthio)phenyl]dihydro-4(1H,3H)-pyrimidinone-2-thione, bis-{2-[dihydro-4(1H, 3H)-pyrimidinone-2-thion-1-yl]phenyl} disulfide, and 3-(2-mercaptobenzothiazol-3-yl)propanoic acid. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 256–261, February, 2006.     

Reaction of 2-methyl-6-p-bromophenyl-3,5-hexadiyn-2-ol with alcohols and ketones

Conclusions The nucleophilic addition of alcohols and ketones to a p-bromophenyldiacetylenic alcohol leads respectively to p-bromophenylenyne ethers and dioxolanes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2827–2829, December, 1974.     

Synthesis of 1,2,4-triazole and thiazole analogs of ketoconazole

The synthesis of 1,2,4-triazole and thiazole analogs of ketoconazole is described in which one of the α azole ring carbons is linked to C-2 of the ketal by means of a three methylene tether. Lithiation of 1-methyl-1,2,4-triazole and thiazole and subsequent alkylation with 2-(2,4-dichlorophenyl)-2-(3-iodopropyl)-1,3-dioxolane produced, after an aqueous acidic workup, 2,4-dichlorophenyl 3-[5-(1-methyl-1,2,4-triazolyl) and 2-thiazolyl]propyl ketones, respectively. Ketalization with glycerol furnished the corresponding diastereomeric pairs of cis and trans 1,3- dioxolanes. The reaction of 2,4-dichlorophenyl 3-[5-(1-methyl-1,2,4-triazolyl)]propyl ketone with 3-mercapto-1,2-propanediol produced the corresponding diastereomeric cis and trans hydroxymethyl 1,3-oxathiolanes. The diastereomeric racemates were separated by column chromatography and their stereochemistry established by nOe nmr experiments. Some of these racemic cis ketal alcohols were converted by benzyl bromide to the corresponding benzyl ethers. Several of these racemic cis-ketals were reacted, first with methanesulfonyl chloride, then with 1-acetyl-4-(4-hydroxyphenyl)piperazine, to furnish the title compounds.     

Cyclische intramolekulare Ester von Äthanolamin-N-methylenphosphonsäuren

The reaction of monoethanolamine with formaldehyde and phosphorous acid gives a mixture of 2-hydroxy-2-oxo-4-phosphonylmethyl-1.4.2-oxazaphospha(V)-cyclohexane and monoethanolamine-N,N-dimethylenephosphonic acid; similarly, diethanolamine, formaldehyde and phosphorous acid yield 2-hydroxy-2-oxo-4-(β-hydroxy-ethyl)-1.4.2-oxazaphospha(V)-cyclohexane along with diethanolamine-N-methylenephosphonic acid.     

Synthesis and properties of 2-(2-oxoindolin-3-ylidene)-2-cyanoacetic acid piperidides and morpholides

The reaction of isatins with cyanoacetic acid piperidide or morpholide gives the corresponding derivatives of 2-(2-oxoindolin-3-ylidene)-2-cyanoacetic acid, which may be reduced to give amides of 2-(2-oxoindolin-3-yl)-2-cyanoacetic acid and react with ethanolic alkali to give quinoline derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No.12, pp. 1611–1613, December 1992.     

2-(3-ethyl-2,2-dimethylcyclobutyl-methyl)-4(3H)-quinazolinones

Anthranilic acid and its 5-bromo and 4-chloro derivatives react with pinanoic and pinonoic acid chlorides to give the corresponding N-acyl derivatives. The pinanoyl derivatives give the corresponding 2-(3-ethyl-2,2-dimethyl-cyclobutylmethyl)-4-(3H)-quinazolinones when refluxed in formamide. Pinanoylanthranilic acid reacts with dicyclohexylcarbodiimide to give 2-(3-ethyl-2,2-dimethylcyclobutylmethyl)benz-3,1-oxazin-4(H)-one and subsequently with hydrazine hydrate to give 3-amino-2-(3-ethyl-2,2-dimethylcyclobutylmethyl)-4(3H)-quinazolinone. Refluxing of the pinanoyl- and pinonoylanthranilic acids with acetic anhydride gives acetylanthranilic acid, and pinonoylanthranilic acid gives 4(3H)-quinazolinone with formamide.Riga Technical University, Riga LV-1658, Latvia; e-mail: marina@osi.lanet.lv. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 811–817, June, 1999.     

Arylierungen von cyclischen Guanidin-Analogen mit α-halogenierten Anthrachinonen: neue Anthrapyrimidine

Arylation Reaction of Cyclic Guanidine-Analogs with α-Halo- anthraquinones: New Anthrapyrimidines 2-Amino-benzimidazole gives on Ullmann-reaction with α-halo-athraquinones such as 1-amino-4-bromoanthraquinone-2-sulfonic acid (la) the new benzimidazo-anthrapyrimidine 2a , whereas 3-amino- triazole gives under the same conditions two products: the 1,2,4-triazoloanthrapyrimidine 7 and l-amino-4-(3-amino-1,2,4- triazolyl)anthraquinone-2-sulfonic acid ( 8 ). The new structures were elucidated by ¹H- and ¹³C-NMR. and X-ray analysis.     

Four-unit linking groups V. Optically active dopants

A number of diesters incorporating a four-unit linking group in the acid part (3-propyloxy, (E)-3-propenyloxy, and 4-butyl units) and an optically active centre in the diol part have been prepared. Structurally related three and four ring dioxolanes derived from the corresponding aldehyde precursors to the acids (i.e., also containing 3-propyloxy, (E)-3-propenyloxy, and 4-butyl groups) and the optically active tartaric acids have also been synthesized. The physical properties of these potential chiral dopants pertinent to electrooptic display device and thermochromic applications have been determined. These new chiral dopants are characterized by short pitches, good solubility in nematic hosts, excellent chemical, photochemical and thermal stability, etc. Most of these new optically active substances are well suited for at least one potential application for a chiral nematic mesophase with exactly denned properties made from a standard nematic mesophase and an optically active dopant. A small number of the new substances exhibit mesomorphic properties at elevated temperatures.