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На основе соединения [S-(R*,R*)]-α-[1-(Метиламино)этил]бензолметанола и α-бромциннамальдегида синтезирован соответствующий 1,3-оксазолидин, строение которого доказано методом ЯМРН спектроскопии, а также изучено влияние его на процесс электровосстановления кислорода (ЭВ О) в различных концентрациях. В качестве метода оценки применена катодная вольтамперометрия на ртутно-пленочном электроде, отражающая количество активных форм кислорода нейтрализованных антиоксидантом за определенное время. Показано, что водный раствор (4S,5S)-2-(1’-бром-2’-фенилвинил)-3,4-диметил-5-фенил-1,3-оксазолидин проявляет антиоксидантную активность в широком диапазоне концентраций. Based on the compound [S- (R*,R*)]-α-[1-(Methylamino)ethyl]benzenemethanol and α-bromocinnamaldehyde, the corresponding 1,3-oxazolidine was synthesized, the structure of which was proved by H NMR spectroscopy, and its effect on the process of electroreduction of oxygen (ER O) in various concentrations. Cathodic voltammetry on a mercury-film electrode, reflecting the amount of reactive oxygen species neutralized by an antioxidant for a certain time, was used as an assessment method. It was shown that an aqueous solution of (4S, 5S)-2-(1'-bromo-2'-phenylvinyl)-3,4-dimethyl-5-phenyl-1,3-oxazolidine exhibits antioxidant activity in a wide range of concentrations.

Pyrazino[1,2-a]indoles fused with various heterocycles, such as oxazolidine, oxazinane, imidazolidine, hexahydropyrimidine and benzimidazole, were synthesized transition metal-free by domino reactions which involved the condensation of 1-(2-bromoethyl)-3-chloro-1H-indole-2-carbaldehydes 28–31 with various nucleophilic amines, resulting in the formation of two new interesting fused heterocycles. The anticholinesterase, antioxidant and antibacterial activities of the compounds were evaluated. Acetylcholinesterase (AChE) inhibitory activities were tested by Ellman’s assay, antioxidant activities were detected using the 2,2-azinobis[3-ethylbenzthiazoline]-6-sulfonic acid (ABTS•+) free-radical scavenging method and antibacterial activities were determined by agar diffusion tests. The oxazolo-pyrazino[1,2-a]indoles (8, 10), the oxazino-pyrazino[1,2-a]indoles (16, 18, 19), the pyrimido-pyrazino[1,2-a]indole (22), and the benzoimidazo-pyrazino[1,2-a]indole (27) possessed the highest inhibitory activity against AChE with IC50 values in the range 20–40 μg mL−1. The oxazolo-pyrazino[1,2-a]indoles (8, 9), the imidazo-pyrazino[1,2-a]indoles (12, 13), and the benzoimidazo-pyrazino[1,2-a]indole (24) revealed the highest antioxidant values with IC50 values less than 300 μg mL−1. However, the oxazolo-pyrazino[1,2-a]indole (11) and imidazo-pyrazino[1,2-a]indoles (12, 13) exhibited weak to moderate bioactivities against all tested Gram-positive bacteria, namely Staphylococcus aureus, Bacillus subtilis and Bacillus cereus.

A diastereoselective (3 + 2) cycloaddition of N-sulfonyl ketimines with vinylethylene carbonates (VECs) in the presence of Pd2dba3·CHCl3 and PPh3 has been developed. The reaction of various substituted VECs and diverse cyclic N-sulfonyl ketimines proceeded smoothly under mild conditions, giving highly functionalized oxazolidine frameworks in good to excellent yields with moderate to good diastereoselectivities. With the use of spiroketal-based diphosphine SKP as a chiral ligand, an asymmetric version of the current (3 + 2) cycloaddition was achieved, and chiral products were obtained in >99% ee in most cases.

A metal-free oxidative cyclization of N-Boc-acrylamides with (diacetoxyiodo)benzene in acetic acid produced 5,5-disubstituted oxazolidine-2,4-diones with the formation of a C-O bond in moderate to excellent yields. In addition, the reaction was diastereospecific with N-Boc-2,3-dimethylacrylamides and proceeded with phenyl migration in the case of an N-Boc-2-phenylacrylamide to generate a 5-acetoxy-5-benzyloxazolidine-2,4-dione.

Herein we describe the PhI(OAc)2-mediated 1,1- and 1,2-difunctionalization of alkenes with N-tosyl amino alcohols to form oxazolidine and morpholine derivatives. This transformation was realized under mild reaction conditions and allows application to various substrates furnishing the multi-substituted oxazolidines and morpholines with yields up to 98%. A deuterium-labeling experiment was carried out and the result indicated that a phenyl group migration occurred to generate oxazolidine products.

The reaction of trimethyl(vinyl)silane 1 and dimethyl(divinyl)silane 2 with various sulfonamides in the oxidative system (tert-BuOCl + NaI) has been studied and shown to be an efficient approach for the synthesis of silylated N-heterocycles. Triflamide demonstrated the reactivity principally different from that of arenesulfonamides. With silane 1, it afforded the products of iodochlorination and bis(triflamidation) (major), whereas arenesulfonamides gave N-arenesulfonylaziridines in up to 91% yield. Silane 2 with arenesulfonamides yielded the products of mono and bis(iodochlorination), mono and bis(aziridination), and 3,5-diiodo-4,4-dimethyl-1-(arylsulfonyl)-1,4-azasilinanes. By contrast, triflamide, apart from the products of halogenation and iodotriflamidation, unexpectedly gave 3-(trifluoromethylsulfonyl)-5-(triflamido)oxazolidine as the main product. The structure of most heterocyclic products is proved by X-ray analysis. The effect of the silyl group in the substrate and of the substituent in the reagent on the course of oxidative sulfamidation is discussed by comparing with all-carbon analogues.

A palladium/copper-catalyzed oxy-carbonation of propargylic amides by halohydrocarbons and CO2 has been developed toward functionalized oxazolidine-2,4-diones. This multi-component reaction (MCR) was triggered by the oxidative addition of RX to Pd(0), followed by the sequential carboxylation of amide and trans-oxopalladation of an electron-deficient triple bond by RPdX species. Finally, the reductive elimination afforded products possessing tetra-substituted vinyl motifs and Pd(0). This protocol features simultaneous formation of three bonds, representing an efficient method for incorporation of CO2 into value-added heterocycles.

DBU mediated 5-exo-dig cyclization of isothiocyanate and propargyl alcohol leading to valuable heterocyclic compounds has been accomplished. The different modes of nucleophilicity (either S-selective or N-selective) of isothiocyanates were found to depend on the substitution pattern of propargyl alcohol. The terminal propargyl alcohol and isothiocyanate underwent an N-nucleophilic attack to afford 3-substituted 4-methylene oxazolidine-2-thiones. In contrast, exclusive S-nucleophilic cyclization was observed with internal propargyl alcohol to produce (Z)-1,3-oxathiol-2-ylidenes and (Z)-N-(Z)-4-ethylidene-1,3-oxathiolan-2-ylidenes from secondary and primary propargyl alcohols, respectively. The formation of high Z-selectivity in the imine motif and alkene is the highlight of this new method as multiple selectivities over C[double bond, length as m-dash]N and C[double bond, length as m-dash]C in a single system are synthetically highly challenging. The Z-selectivity in imine and alkene may be attributed to electronic and steric factors respectively.

The asymmetric unit of the crystal of the title compound contains two rivaroxaban mol­ecules with different conformations., The asymmetric unit of the crystal of the title compound (common name rivaroxaban), C19H18ClN3O5, contains two rivaroxaban mol­ecules with different conformations; the C—C—N—C torsion angles between the oxazolidine and thio­phene rings are −171.1 (7) and −106.8 (9)° in the two independent mol­ecules. In the crystal, classical N—H⋯O hydrogen bonds and weak C—H⋯O hydrogen bonds link the mol­ecules into a three-dimensional supra­molecular architecture.

Ru-catalyzed directed o-C–H arylation reactions of 2-phenylpyridine, N-phenylpyrazole, acetophenone N-(p-methoxyphenyl)imine, and 2-phenyloxazoline proceed in good to excellent yields with a number of functionalized aryl and heteroaryl bromides in neat Bu4NOAc at 120 °C. The acetate ion acts as the base and the relatively low melting point Bu4N salts (a mixture of acetate and bromide) behave as an ionic liquid. Arylation reactions of 2-phenyloxazoline proceed with concomitant oxazolidine cleavage to give 2-(N-acetylamino)ethyl benzoates promoted by side product CH3COOH. The dual-purpose ionic liquid medium is compatible with both ligandless Ru for di-arylation (optimal pre-catalyst: RuCl3·xH2O) and Ru-phosphane (optimal pre-catalyst: [RuCl2(p-cymene)]2/P(p-Tol)3 1:4) catalysts (1–5 mol-%) for selective mono-arylation.

A new synthetic route to N-alkyl-2-acylazetidines was developed through a highly stereoselective addition of organolithiums to N-alkyl-2‐oxazolinylazetidines followed by acidic hydrolysis of the resulting oxazolidine intermediates. This study revealed an unusual reactivity of the C=N bond of the oxazoline group when reacted with an organolithiums in a non-polar solvent such as toluene. The observed reactivity has been explained considering the role of the nitrogen lone pair of the azetidine ring as well as of the oxazolinyl group in promoting a complexation of the organolithium, thus ending up with the addition to the C=N double bond. The high level of stereoselectivity in this addition is supported by DFT calculations and NMR investigations, and a model is proposed for the formation of the oxazolidine intermediates, that have been isolated and fully characterized. Upon acidic conditions, the oxazolidine moieties were readily converted into 2-acylazetidines. This synthetic approach has been applied for the preparation of highly enantioenriched 2-acylazetidines starting from chiral not racemic N‐alkyl-2‐oxazolinylazetidines.

Transformations of α-hydroxyphosphonates derived from proline or serine by treatment with different deoxyfluorinating reagents (DAST, Deoxofluor, PyFluor) are reported. Depending on the applied reagent, as well as the protecting group used (N-Cbz, N-Boc, N-Bn) different types of products are observed. The reaction of N-Cbz or N-Boc prolinols with DAST or Deoxofluor due to aziridinium intermediate participation gave fluorinated amino phosphonates such as piperidine and pyrrolidine derivatives and/or oxazolidine-2-ones. Similarly, the analogous reaction of N-Cbz or N-Boc protected serinol yielded oxazolidine-2-ones or its fluorinated analogues. As the second type of product formed by DAST-induced reaction of serine derivatives, aziridines were obtained. Only in the case of deoxyfluorination of N-benzyl prolinols were both diastereoisomers of β-fluoropiperidine-α-phosphonates formed, while the reaction of protected N-benzyl serinols gave fluorinated oxazolidines. Moreover, application of PyFluor gave sulfonate derivatives.

A dual catalytic system, dirhodium tetrapivalate/ytterbium(III) triflate, enables the three-component reactions of α-alkyl-α-diazoesters, aromatic aldehydes, and N-benzylidenebenzylamine derivatives to afford the corresponding β-amino alcohols in good yields after hydrolysis of the oxazolidine cycloadducts, whereas no β-amino alcohols are obtained in the absence of ytterbium(III) triflate. A similar dual catalytic system, dirhodium tetraacetate/ytterbium(III) triflate, is found to be effective in accelerating the reactions of α-aryl-α-diazoesters in high yields. Furthermore, the reactions using dimethyl diazomalonate are described.

Condensation of N-(2-hydroxyethyl)ethylenediamine and pyridine-2-carbaldehyde in the presence of ZnX2 salts (X = ClO4−, Cl−, Br−, I−) generates four complexes, namely, [ZnL1Cl](ClO4) (1), [ZnL1Cl][ZnCl3(H2O)]·2H2O (2), [ZnL1Br][ZnBr3(H2O)]·2H2O (3), and [Zn(L2)3]I2 (4), where L1 and L2 are aminal and hemiaminal ether derivatives, i.e., (E)-N-((pyridine-2-yl)methylene)-2-((2-pyridine-2-yl)oxazolidin-3-yl)ethanamine and 2-(2-pyridin-2-yl-imidazolidin-1-yl)-ethanol, respectively. No complex with the expected Schiff-base ligand (E)-2-(2-(pyridin-2-ylmethyleneamino)ethylamino)ethanol (L) or with 2-(2-pyridyl-3-(2-hydroxyethyl))oxazolidine (L3) was obtained. The structures of complexes 1, 3, and 4 have been elucidated by single crystal X-ray diffraction. All the complexes have been characterized by detailed NMR (1H, 13C and DEPT-135) and ESI-MS analyses, indicating retention of solid state structures in the solution phase. Complex 1 deserves special mention as during its formation, the ClO4− ion undergoes reduction to Cl− and thus, it forms a mixed anionic ligand complex. Thorough DFT calculations have been performed at the BP86-D3/def2-TZVP level of theory to rationalize the ligand and complex formation. The calculations suggest that the aminal form (L1) is the most favored species followed by the Schiff-base, whereas the hemiaminal ether form (L3) is the least preferred one. The role of halides during the formation of the monoanionic [ZnX3(H2O)]− species is crucial, and the achieved complex is highly favored when X = Cl and disfavored for X = I; this trend has been rationalized by the DFT calculations. The phosphatase activities of the complexes have been investigated, and their efficiencies follow the order 2 > 1 > 3 > 4.

Synthesis of 3-fluoro-2-hetarylindoles through addition of hetarenes to 3,3-difluoroindolium ions generated in situ by Zn(OTf)2-catalyzed oxazolidine ring opening is described. Indoles, pyrroles and alkyl-substituted furans can be used as hetaryl nucleophiles to afford a range of 3-fluoro-2-hetarylindole products 6 in 56–95 % yields. A diverse array of 3,3-difluorinated 2-hetarylindolines 7 can also be synthesized in 43–84 % yields by a tandem sequential process that involves hetarene nucleophilic addition, HF elimination and fluorocyclization reactions. Our study by 1H NMR and UV/Vis spectroscopy reveals that 3,3-difluorinated 2-hetarylindolines possess interesting substituent-dependent acidochromic properties. UV absorption and fluorescence spectra of selected compounds 6 and 7 are also studied.

Diastereoselective addition of nitromethane to Boc-D-Phe-H in the presence of sodium hydride in diethyl ether/hexane containing 15-crown-5 and subsequent N,O-protection with 2,2-dimethoxypropane gave trans-oxazolidine in a diastereomeric ratio of >16:1. The oxazolidine was easily separated by column chromatography, which after Nef reaction was coupled to H-Leu-OtBu. The 8-step synthesis afforded (-)-bestatin in an overall yield of 24.7% after deprotection and ion exchange.

Catalytic asymmetric Friedel–Crafts reaction of indoles with nitroalkenes was catalyzed by the stereochemically tunable bis(oxazolidine)pyridine (PyBodine)–Cu(OTf)2 complex. Using the PyBodine(Val)–Cu(OTf)2 catalyst gave the Friedel–Crafts ­adducts with highly enantioselective manner. For the 1,4-bis[(E)-2-nitrovinyl]benzene, the reaction proceeded in a meso-trick manner to give the chiral double Friedel–Crafts adduct with 97% enantiomeric excess.

Phenyl oxazolidinones were prepared from R - glycidyl butarate and Para bromo aniline, further (3 - (4 - bromophenyl) methylene oxazolidine - 5yl) and substituted benzothiazinen was refluxed resulted in oxazoli dinones benzothiazinen moieties. Treatment of these oxazolidinones benzo thiazinen moieties with methane sulfonyl gives its sulphonates on further treatment with sodium azide and tri phenyl phosphine in acetic anhydride gives acetamide derivatives . Further synthesized compounds were characterized by IR, H NMR 1 and Mass spectral studies. T he synthesized compounds were evaluated for antibacterial activity against Bacillus subtilis , Staphylococcus aureus , Escherichia coli , Pseudomonas aeruginosa and antifungal activity against , Candida albicans and Aspergillus

A convenient one-pot method for the preparation of (4Z)-4-(arylmethylidene)-5-ethoxy-1,3-oxazolidine-2-thiones 2 and 3 from ethyl (2Z)-3-aryl-2-isothiocyanatoprop-2-enoates 1, which can be easily prepared from ethyl 2-azidoacetate and aromatic aldehydes, has been developed. Thus, these α-isothiocyanato α,β-unsaturated esters were treated with organolithium compounds, including lithium enolates of acetates, to provide 5-substituted (4Z)-4-(arylmethylidene)-5-ethoxy-1,3-oxazolidine-2-thiones, 2, and 2-[(4Z)-(4-arylmethylidene)-5-ethoxy-2-thioxo-1,3-oxazolidin-5-yl]acetates, 3.

The efficient formation of a bicyclic oxazolidine by lithium aluminium hydride reduction of a tertiary amide provides an example of intramolecular nucleophilic capture of an iminium ion equivalent by the oxygen of a silyl ether.

Simple and efficient strategies toward the synthesis of trisubstituted pyrrolizidines and disubstituted oxazolidine systems by 1,3-dipolar cycloaddition reactions using arylaldehydes and α-amino acids have been developed, followed by a one-pot, three-component strategy. Electron-deficient dipolarophiles, chalcones, were reacted with nonstabilized azomethine ylides derived from arylaldehyde and L-proline in dry dimethyl formamide, leading to substituted pyrrolizidines. The route to substituted oxazolidines involved cycloaddition to the C˭O bond of a second molecule of the aldehyde. The structures and stereochemistry of the cycloadducts were established by infrared (IR), NMR spectroscopy, and single-crystal x-ray crystallographic analyses. Condensed Fukui functions and local electrophilicity indices have been computed to characterize the reactive sites and predict the preferred interactions of azomethine ylides to planar chalcones. The softness-matching indices have been evaluated to determine the r...

The reaction of proline with benzaldehyde leads to oxapyrrolizidines (III)/(IV), which are convenient building blocks for the synthesis of 2-substituted pyrrolidines via oxazolidine ring opening by treatment with Grignard reagents and subsequent removal of the N-hydroxy(diphenyl)ethyl moiety.

In the reaction of N , N ′-methylenebis[(4 S ,5 R )-4-methoxycarbonyl-5-methyloxazolidine] ( 1 ) with CuCl 2 or RuCl 3 in alcoholic solvents novel complexes, bis[(4 S ,5 R )-4-methoxycarbonyl-5-methyl-1,3-oxazolidine]copper(II) dichloride ( 2 ) and bis[(4 S ,5 R )-4-methoxycarbonyl-5-methyl-2-oxazoline]-(4 S ,5 R )-4-methoxycarbonyl-5-methyl-1,3-oxazolidineruthenium(III) trichloride ( 3 ), respectively, were isolated and fully characterized by X-ray crystallography. In these reactions, which occurred under mild conditions, ligand 1 was cleaved at the bridging aminal position and degraded to (4 S ,5 R )-4-methoxycarbonyl-5-methyl-1,3-oxazolidine 5 . The trigonal bipyramidal Cu complex 3 contains two such oxazolidine ligands coordinated in different ways. One is bonded in a monodentate fashion via the nitrogen atom of the five-membered ring, the other binds as a bidentate ligand, additionally using the carbonyl oxygen of the ester group. In the octahedral Ru complex 4 there are one oxazolidine ligand 5 and two oxazoline ligands 6 . Thus, in the synthesis of 4 the carbon atom between oxygen and nitrogen in the oxazolidine ring was partly oxidized from the half-aminal status to the carboxamide status.

Conjugate addition of thiazolidinethiones and oxazolidinethiones to N-crotonylthiazolidinethiones and -oxazolidinethiones was observed in the presence of excess triethylamine in dichloromethane. The addition takes place by the nitrogen of the heterocycle with high diastereoselectivity. It was observed that the stereoselective addition occurs on the anti-s-cis conformation of the N-enoyl sulfur-containing heterocycle.

The alkylation reactions of an amide sodium enolate derived from a C-2 disubstituted trifluoromethylated oxazolidine (Fox) chiral auxiliary occurred in good yields with a very high diastereoselectivity (>98% de). Compared to the C-2 monosubstituted trifluoromethyl analogue, this chiral auxiliary is much more stable towards bases at temperature over −35 °C because the dehydrofluorination reaction is avoided. However asymmetric enolates quaternarization was not successfully achieved with this new chiral auxiliary.

Selective saturation of the conjugated C–C double bonds in the title compounds was examined in a systematic way for the first time. Many established protocols effective for similar reduction of α,β-unsaturated ketones and esters in the literature were found to be inapplicable in the present context. The most satisfactory results were finally obtained using the DIBAL-H/MeLi/CuI/HMPA/THF conditions.

The 3-phenyl-2-(pyridin-2-yl)oxazolidine ligand (ppo) was synthesised and its coordination behaviour regarding Ni(II) and Pd(II) centres was studied. The reaction with K(2)PdCl(4) affords [Pd(N,N'-ppo)Cl(2)] (1), in which ppo binds to palladium via the pyridyl nitrogen and the oxazolyl nitrogen atoms. On the contrary, reaction with NiCl(2)·6H(2)O produces [Ni(N,O-ppo)(2)Cl(2)] (2), in which two ppo ligands are coordinated via the pyridyl nitrogen and the oxygen atom of the oxazolidine ring. The X-ray diffraction analysis of the complexes confirms a square planar geometry for Pd(II) in 1 and an octahedral configuration around Ni(II) in 2, which, to the best of our knowledge, represents the first reported example of a structurally characterised nickel-oxazolidine compound. In addition, both complexes prove to be active catalysts under mild conditions in the aza-Michael reaction of (E)-4-phenylbut-3-en-2-one (benzalacetone) with aliphatic amines.

A nonstabilized azomethine ylide reacts with a wide range of substituted isatoic anhydrides to afford novel 1,3-benzodiazepin-5-one derivatives, which are generally isolated in high yield. The transformations involve 1,3-dipolar cycloaddition reactions of the ylide with the anhydrides to give transient, and in a representative case spectroscopically observable, oxazolidine intermediates that undergo ring-opening-decarboxylation-ring-closing reaction cascades to yield the 1,3-benzodiazepin-5-one products.

A wide range of aliphatic and aromatic α-keto esters has been transformed to α-hydroxy-β-nitro esters via the Cu(II)-bisoxazolidine-catalyzed Henry reaction. In the presence of 10 mol% of the chiral catalyst, nitroaldol products were obtained in up to 95% yield and 76% ee.

Diphenylphosphinoethane (DPPE)-catalyzed and ZnI2-promoted in situ formation of oxazolidine, alkynyl zinc, and propargylamine intermediates from 1-alkynes, chiral (S)-diphenyl(pyrrolidin-2-yl)methanol, and propiolates gave the corresponding chiral (R)-β-allenoates in 40–72% yield with up to >99% ee. The intermediate propargylamine was isolated in 50% yield and converted to give the β-allenoate 10aa in 68% yield and 96% ee upon reaction with ZnI2. The results are discussed considering a mechanism involving oxazolidine and iminium ions formed in situ followed by addition of alkynyl zinc complex to produce the propargylamine that gives the corresponding allenoate via a 1,5-hydrogen shift in the presence of ZnI2.

One-pot Prato reactions of C60 with amino acids and aldehydes afford five new fullerene derivatives, including two unexpected thiazolidine and oxazolidine fulleropyrrolidines. In particular, L-cysteine (1), paraformaldehyde and C60 in refluxing toluene solution affords an unexpected new thiazolidine-fulleropyrrolidine derivative 3 (instead of 2) via 1,3-dipolar cycloaddition, whose structure was characterized in detail. A possible reaction mechanism for the formation of 3 is proposed. These suggest that the active hydrogen of S–H in 1 is essential for the formation of the thiazolidine ring in 3. To confirm further this conclusion, reactions of C60 with different amino acids (5, 7) and aldehydes (3-(methylthio)proplonaldehyde (9) and 2-thiophenaldehyde (11)) were also studied, resulting in the synthesis of other three new thio-derivatives of C60 (6, 10, 12) as well as an oxazolidine fulleropyrrolidine (8).

Condensation of N-substituted 3-azabicyclo[3.3.1]nonan-9-ones with difunctional N,N-, N,S-, and N,O-centered nucleophiles (o-phenylenediamine, 1,2-diphenylethane-1,2-diamine, 2-aminobenzenethiol, cysteine, 2-aminophenol, serine) gave the corresponding spiro heterocyclic compounds fused at the C9 atom. Treatment of N-tert-butoxycarbonyl-substituted spiro compounds with anhydrous hydrogen chloride resulted in elimination of the tert-butoxycarbonyl group with formation of spiro[3-azabicyclo[3.3.1]nonane-9,2′-azole] hydrochlorides.

The kinetic and thermodynamic parameters of the Hg(II)-catalyzed cyclization of N-phenyl-2-vinyloxyethanamine indicated that the first reaction step is reversible coordination of mercury at the vinyloxy group, followed by closure of mercurated oxazolidine ring (the rate-determining step); the latter undergoes demercuration to give 2-methyl-3-phenyloxazolidine either by the action of mercury salt anion or spontaneously.

Two classes of diastereomerically enriched chiral tridentate ligands incorporating either two oxazolidine and one pyridine ( 1) or two pyridine and one oxazolidine ( 2a-c) donor groups have been made in a high-yielding modular fashion from readily available enantiopure amino alcohols and aldehydes. Both ligand classes readily formed metal complexes via 1:1 reactions with trans-PdCl 2(PhCN) 2. The compounds Pd( 1)Cl 2 and Pd( 2a-c)Cl 2 were formed as mixtures of 3 and 2 diastereomers, respectively, owing to indeterminate absolute configuration at the C (2) position of their constituent oxazolidine rings. Within each diastereomeric manifold, the metal complexes existed as equilibrium mixtures of bi- and tridentate isomers in solution, the interconversion between which was very rapid even at -50 degrees C. The fluxional nature of the compounds was inferred from a combination of (1)H and (15)N NMR spectroscopic and solution conductivity data. Substitution of one chloride ligand for hexafluorophosphate gave as mixtures of diastereomers the salts [Pd( 1-kappa N,kappa (2) N')Cl]PF 6 ( 8) and [Pd( 2a-c-kappa N,kappa N',kappa N'')Cl]PF 6 ( 12a-c) in which the ligands were coordinated through all three N-donors. A single recrystallization of 8 gave in optically pure form the major diastereomer 8 ( maj ), which was characterized crystallographically. Complexes of 2a-c differed substantially from those of the bis(pyridylmethyl)amine (bpma) ligand family with which they shared direct atom-for-atom connectivity in the coordinating groups. The amines are known to form exclusively the static tridentate complexes [PdCl(bpma-kappa N,kappa (2) N')]Cl; the difference was attributed to torsional strain associated with the rigid oxazolidine ring in tricoordinated 2a-c.

Axially chiral 5,5-dimethyl-3-( o -aryl)rhodanine, 3-( o -aryl)rhodanine and 5,5-dimethyl-3-( o -aryl)-2-thioxo-4-oxazolidinone derivatives have been synthesized as racemates and the energy barriers to enantiomerization have been determined by dynamic 1 H NMR or by following the thermal equilibration of the separated enantiomers using chiral HPLC. The barriers to rotation about the N sp2 –C aryl single bond were found to be 82–129 kJ/mol. The racemization barriers in these compounds are affected by the size of the ortho -substituent on the aryl ring. The magnitude of the barriers was found to change linearly with the van der Waals radii of the ortho -halogen substituents.

(4S)-N-Boc-4-fluoro-l-proline methyl ester (4) was prepared from the following sequence of reactions: esterification of trans-4-hydroxy-l-proline (2), Boc protection, and fluorination by DAST. Reaction of 4 with lithiated oxadiazole provided oxadiazolyl ketone 7. Deprotection of the Boc group of 7 and subsequent coupling with bromoacetyl bromide gave bromide 9. Coupling reaction of 9 with excess oxazolidine 16 provided coupled product 17. Unexpectedly, the stereogenic center of 17 was completely epimerized to a virtually 1:1 mixture of cis- and trans-17 at this stage. After the deprotection of the N,O-methylene acetal group of 17 using aqueous ammonium chloride, crystallization induced dynamic resolution (CIDR) of cis- and trans-mixture of LC15-0133 (1) in the course of tartrate salt formation provided cis-LC15-0133 (1a) tartrate salt in 83% yield (>98% de).

The influence of 1,3-oxazolidine and 1,3-oxathiolane fragments in substituted alkenes on the direction of their catalytic reaction with diazomethane has been investigated. The olefins bearing an oxazolidine substituent in the α- or γ-position and an oxathiolane substituent in the γ-position relative to the C=C bond react with diazomethane in the presence of Pd(acac)2 selectively resulting in cyclopropanation products. The use of Cu(OTf)2 does not result in cyclopropanation; however Cu(OTf)2 catalyzes the reaction of diazomethane with 2-(alk-1-enyl)-1,3-oxathiolanes yielding 2,3,5,6-tetrahydro-1,4-oxathiocines formed through the [2,3]-sigmatropic rearrangement of the intermediate sulfonium ylides.

The condensation products of 2-aminoethanol or 3-aminopropanol (bearing an alkyl substituent on the carbon adjacent to the nitrogen) with substituted benzaldehydes proved to exist in CDCl3 at 300 K as threecomponent tautomeric mixtures of the diastereomeric five- or six-membered 1,3-O,N-heterocyclic ring forms and the corresponding imines. For each equilibrium, the electronic effects of the 2-aryl substituents were characterized by the Hammett equation. The steric effects of the alkyl groups could be described by Hansch-type equations for the equilibria involving oxazolidine ring forms. While the alkyl substituents did not cause any significant effect on the ring cis-chain and the ring trans-chain equilibria for tetrahydro-1,3-oxazines, increasing bulk of the 4-alkyl group increased the stability of the cyclic tautomers for the analogous oxazolidines.

The reaction of 1-(4-tolylthio)-, 1,1-bis(4-tolylthio)-, or 1,1,3-tris(4-tolylthio)perchloro-2-nitro- 1,3-butadiene with α,β-bifunctionalized ethanes such as N,N-, N,O,-, N,S-, O,S-, S,S-, or O,O- bisnucleophiles leads to both, highly functionalized 2-(1-nitroallylidene) derivatives of imidazolidine, oxazolidine, thiazolidine, (1,3)oxathiolane, or (1,3)dithiolane, respectively, and to the open chain, next higher thiolated buta-1,3-diene. The product distribution is highly sensitive to modifications of the reaction conditions: apart from changes of molar ratios of substrates and reagents the reaction temperature plays an important role. Thus, increase of the reaction temperature favours formation of the 1,3-heterocyclic ring. In all cases, extensive spectroscopic investigations have been performed and, in the case of the (1,3)oxathiolane also an X-ray analysis.

Starting from tetrabutylammonium 2,2-diphenylglycinate and (hetero)aromatic aldehydes the reaction provides a mixture of syn- and anti-2-iminoalcohols, the syn-isomer of which exists in an equilibrium with its oxazolidine tautomer.

The process leads to formation of oxazolidine structures in moderate yields and good to excellent diastereoselectivity.

International audience; This work presents an original strategy to modulate the electrochemical properties of the indolino[2,1-b]oxazolidine core appropriately substituted in position 5 (para-substitution of the phenyl ring) by acceptor or donor groups (CHO, OMe, Me, F, H, Cl, Br). Supported by spectroelectrochemical experiments and confronted to electrochemical simulations, the stepwise oxidation of indolino[2,1-b]oxazolidine derivatives involves an electrochemical mechanism which depends on the para-substitution of the phenyl ring and leads to either the formation of a stable radical cation, the opening of the oxazolidine ring or an irreversible aryl C–C coupling.

In this study we compare spectroscopic properties of pemoline (2-amino-5-phenyl-2-oxazolin- 4-one) and its acid hydrolysis product 5-phenyl-oxazolidine-2,4-dione. Crystallization of pemoline from aqueous acetic acid gave single crystals of compound 2, the structure of which was determined by X-ray studies. All four crystallographically independent molecules form dimers linked by N-H···O = C hydrogen bonds.

The existence of two types of intramolecular cation-π interactions between a phenyl and a pyridinium, and between a thiocarbonyl and a pyridinium in nicotinic amide derivatives have been clarified by 1H NMR and CD spectroscopies, X-ray structural analysis and calculations.These interactions resulted in the shielding of one side of the pyridinium face by the phenyl or the thiocarbonyl group, which enables nucleophiles to attack the pyridinium ring from the opposite side. Addition of organometallic reagents and ketene silyl acetals gave 1, 4-dihydropyridines in high regio- and stereoselectivities. The stereochemistry of the chiral center of the products was opposite depending on whether the chiral auxiliary is oxazolidine or thiazolidine-2-thione.Moreover, the DMAP derivatives bearing a thiazolidine-2-thione moiety served as asymmetric acylating catalysts. Kinetic resolution of a variety of sec-alcohols was performed in the presence of 0.5 mol% of the catalyst with the s values of 7-30.