A stereochemical investigation of 2-methyl- and 2,5-dimethyl-3-phenyl-1,3-oxazolidines using NMR

The stereochemical properties of two 2-methyl-3-phenyl-1,3-oxazolidines and two of its 5-methyl substituted and four of its 2,5-dimethyl substituted derivatives have been investigated by pmr and cmr methods. The compounds of 2,5-dimethyl-3-phenyl-1,3-oxazolidines exist in isomeric cis and trans forms at the two methyl groups on the heterocyclic ring.     

Mass-spectrometric study of 1,3-oxazacyclopentanes

The fragmentation of 1,3-oxazolidines under electron-impact and chemical-ionization (with methane as the gas reagent) conditions and the effect of the substituent in the 2 position of the heteroring on the stability of the molecular ions (M⁺) and on the character of the fragmentation of 1,3-oxazolidines were studied. It is shown that splitting out of an alkyl group from the 2 position is characteristic for electron impact. Processes involving alkylation and protonation with the formation of cluster ions are most characteristic for chemical ionization. In analogy with hydrolysis in the condensed phase, protonated 1,3-oxazolidine molecules split out an aldehyde molecule.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1031–1034, August, 1981.     

Synthesis of 2,3-disubstituted-1,3-oxazolidines

A series of 2-aryl-3-alkyl or aryl carbamoyl- and thiocarbamoyl-1,3-oxazolidines was prepared by the reactions of alkyl and aryl isocyanates and isothiocyanates with N-(2-hydroxyethyl)-benzalamincs. The nuclear magnetic resonance spectra of these compounds are discussed.     

Oxidation of 1,3-Dioxacycloalkanes with Complexes of Potassium Chlorochromate and Chlorodiperoxochromate with 15-Crown-5, Catalyzed with 2,2,5,5-Tetramethyl- 4-phenyl-3-oxo-3λ5-imidazolin-1-yloxyl

2,2,5,5-Tetramethyl-4-phenyl-3-oxo-3⁵-imidazolin-1-yloxyl catalyzes oxidation of 2-isopropyl-1,3-dioxolane, 2-phenyl-1,3-dioxolane, 2-phenyl-4-chloromethyl-1,3-dioxolane, and 2-phenyl-1,3-dioxane with 15-crown-5 complexes of potassium chlorodiperoxochromate (KCrO₅Cl·2C₁₀H₂₀O₅) and potassium chlorochromate (KCrO₃Cl·2C₁₀H₂₀O₅). 2-Isopropyl-1,3-dioxolane is oxidized to the corresponding monoester in quantitative yield, and the 2-phenyl derivatives yield benzaldehyde. The spiro ketal, 2,2-pentamethylene-4-methyl-1,3-dioxane, is decomposed to cyclohexanone.     

C(6)N(7)-cyclized purines

By reaction of 6-[N-(2-hydroxyethyl)-N-methyl]aminopurine ( 2a ) and of the corresponding 3-hydroxypropyl derivative 2b with thionyl chloride a bridge to N(1) is formed yielding 5 and 6 , respectively, whereas from 6-[N-(4-hydroxybutyl)-N-methyl]aminopurine ( 2c ) the 4-chlorobutyl compound 4 is obtained, which cyclizes in alkaline medium to the C(6)-N(7) bridged compound 7 . A related cyclization to 11a–11f is observed when 6-chloropurines are reacted with 3-alkyl-1,3-oxazolidines or 3-methyl-1,3-thiazolidine.     

Phenylselenium Trichloride,Preparation and Use as a Vinylic Chlorination Reagent

Phenylselenium trichloride (1) is prepared from benzeneseleninic acid (2) and thionyl chloride and used to effect vinylic chlorination, viz. the conversion of 3-chloro-2-chloromethyl-1-propene (4) into 2-chloromethyl-1,3-dichloro-propene (3).     

Investigation of substituted 1,3-oxazolidines using 1H and 13C NMR spectroscopy

The characteristics of the ¹H and ¹³C NMR spectra of 1,3-oxazolidines with substituents in the 2-, 3-, and 5-positions have been studied. The relation of the spectral characteristics to the structure and configuration of the compounds has been examined, and information on the transmission of the substituent effect through the atoms of nitrogen and oxygen has been obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1255–1260, September, 1986.     

Synthesis of 2-functionally substituted oxazolines and oxazolidines from methyl bromopropiolate and Β-amino alcohols

The reaction of methyl bromopropiolate with -amino alcohols containing a primary amino group generally results in the formation of 2-(methoxycarbonylmethyl)-²-1,3-oxazolines, while in the reaction with N-methyl- and N,N-dimethyl-substituted -aminoalcohols, 2-(methoxycarbonylmethylene)-1,3-oxazolidines, or their salts are formed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 406–409, March, 1991.     

Diastereoselective addition of organolithiums to 1,3-oxazolidines complexed with aluminum tris(2,6-diphenylphenoxide) (ATPH)

1,3-Oxazolidines were easily obtained by condensation of N-substituted (R)-phenylglycinol with aldehydes. Addition of organolithium reagents to 1,3-oxazolidines by complexation with the bulky Lewis acid aluminum tris(2,6-diphenylphenoxide) (ATPH) readily produced the corresponding chiral amines with good yield and high diastereoselectivity. The configuration of the new stereogenic center was shown to be opposite to that of adducts obtained for the same 1,3-oxazolidines using Grignard reagents. The best diastereoselectivity was achieved using N-isopropyl-1,3-oxazolidines. The mechanism of addition was deduced by determining the stereochemistry of the iminium-aluminum complex by NOE experiments.     

Synthesis and crystal structure of (2<Emphasis Type="Italic">S</Emphasis>,4<Emphasis Type="Italic">S</Emphasis>,5<Emphasis Type="Italic">R</Emphasis>)-2-(5-bromo-2-hydroxyphenyl)-3,4-dimethyl-5-phenyl-1,3-oxazolidines

Condensation of ephedrine alkaloids with 5-bromo-2-hydroxybenzaldehyde was studied, and X-ray diffraction analysis of the synthesized (2S,4S,5R)-2-(2-hydroxy-5-bromophenyl)-3,4-dimethyl-5-phenyl-1,3-oxazolidines was performed.     

Zur Reaktion von 1,3-Oxazolidinen mit Dicarbonsäureanhydriden

Reaction of 3-methyl-1,3-oxazolidine with phthalic anhydride in chloroform leads to ring opening and higher oligomers2 are formed. These are cleaved by addition of protic solvents and 2-methylaminoethyl hydrogenphthalate3 a is obtained. Other 1,3-oxazolidines and succinic anhydride behave similarly.

Herrn Prof. Dr. Dr. h. c.Karl Kratzl mit den besten Wünschen zum 70. Geburtstag gewidmet.     

Regioselectivity of the hydrolysis of 2-(1-alkoxyvinyl)-substituted imidazolidines, 1,3-thiazolidines,and 1,3-oxazolidines

2-(1-Alkoxyvinyl)-1,3-thiazolidines reacted with H₂O or D₂O in the presence of 105 mol % of p-toluenesulfonic acid or trifluoroacetic acid (20°C, 1 h) to give 2-acetyl-1,3-thiazolidine in quantitative yield. 2-(1-Alkoxyvinyl)-3,5-diphenylimidazolidines underwent hydrolysis in the presence of 20 mol % of an acid (20°C, 24 h) at the vinyloxy group with high regioselectivity yielding 2-acetylimidazolidines. Hydrolysis of 2-(1-alkoxyvinyl)-3-phenyl-1,3-oxazolidines in the presence of 10 mol % of p-toluenesulfonic acid (20°C, 5 days) takes two pathways, one of which involves the endocyclic C-O bond with ring opening and the other involves the vinyloxy group to produce 2-acetyl-3-phenyl-1,3-oxazolidine. Unlike phenyl-substituted 1,3-thiazolidines and imidazolidines, hydrolysis of their 3-methyl- and 3,5-dimethyl-substituted analogs in acid medium occurs mainly via ring opening. The observed hydrolysis pathways were interpreted in terms of B3PW91/6-311G(d,p) quantum-chemical calculations.     

Rh2(oac)4-catalyzed reactions of methyl diazoacetate with 1,3-oxazolidines and 1,3-oxathiolanes

Methoxycarbonylcarbene generated by catalytic decomposition of methyl diazoacetate in the presence of Rh₂(OAc)₄, is regioselectively inserted into the C(2)-O bond of 3-alkyl-2-phenyl-1,3-oxazolidines and into the C(2)-S bond of 2-phenyl-1,3-oxathiolane. Study by the competitive reaction method demonstrated that the relative reactivity toward the insertion of the methoxycarbonylcarbene fragment into the C-heteroatom bond increases in the series of 1,3-dioxolane, 1,3-oxazolidine, and 1,3-oxathiolane. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1411–1415, August, 2006.     

Catalytic diversity of diene complexes of niobium and tantalum on polymerizations of ethylene,norbornene, and methyl methacrylate

Half‐metallocene diene complexes of niobium and tantalum catalyzed three‐types of polymerization: (1) the living polymerization of ethylene by niobium and tantalum complexes, MCl₂(η⁴‐1,3‐diene)(η⁵‐C₅R₅) ( 1‐4 ; M = Nb, Ta; R = H, Me) combined with an excess of methylaluminoxane; (2) the stereoselective ring opening metathesis polymerization of norbornene by bis(benzyl) tantalum complexes, Ta(CH₂Ph)₂(η⁴‐1,3‐butadiene)(η⁵‐C₅R₅) ( 11 : R = Me; 12 : R = H) and Ta(CH₂Ph)₂(η⁴‐o‐xylylene)(η⁵‐C₅Me₅) ( 16 ); and (3) the polymerization of methyl methacrylate by butadiene‐diazabutadiene complexes of tantalum, Ta(η²‐RN=CHCH=NR)(η⁴‐1,3‐butadiene)(η⁵‐C₅Me₅) ( 25 : R = p‐methoxyphenyl; 26 : R = cyclohexyl) in the presence of an aluminum compound ( 24 ) as an activator of the monomer.     

Comparison of Conventional and Microwave Assisted Reactions Giving Aromatic Oxazolidines

By reaction of aromatic aldehydes with (-)-ephedrine aromatic 1,3-oxazolidines can be obtained. The reaction was carried out either at conventional conditions or by microwave heating. The different diastereomeric ratios were determined by means of ¹H NMR spectroscopy.     

Highly diastereoselective N-nitrosation of chiral (E)-2-(benzylidene-amino)ethanols with nitric oxide

N-Nitrosation of (E)-(S)-2-(benzylidene-amino)ethanols 2 with nitric oxide occurred highly diastereoselectively, to give the (2S,4S)-diastereomer dominant N-nitroso-(2S,4S)-1,3-oxazolidines in good yield. Intermediate 2 was prepared from the reaction of benzaldehyde 1 with (S)-2-aminoethanol.     

Synthesis and fungicidal activities of 1-[(2,2-diaryl-1,3-dioxolan-4-yl)methyl]-1H-azoles

Ketalization of benzophenones with epichlorohydrin or 3-chloropropane-1,2-diol gave 2,2-diaryl-4-chloromethyl-1,3-dioxolanes, which were used to alkylate sodium salts of imid-azole or 1,2,4-triazole. The resulting 1-[(2,2-diaryl-1,3-dioxolan-4-yl)methyl]-1H-azoles exhibit high fungicidal activities. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 940–944, May, 2007.     

Investigation on radical polymerization of 2-methylene-1,3-dioxolanes and 2-methylene-1,3-oxazolidines

The reaction of 2-methylene-1,3-dioxolanes and 2-methylene-1,3-oxazolidines with benzoyl peroxide (acceptor radical) and with N-ethylmaleimide (acceptor) was investigated. It was shown that benzoyl peroxide adds to monomers 1a and 1b , giving the corresponding linear diester amides 1a and 1b respectively. The oxazolidine 1c adds benzoyl peroxide, without ring opening, by addition to the exomethylene group. Together with N-ethylmaleimide the oxazolidines 1a or 1b produce deep-colored charge transfer complexes, resulting in high molecular poly-N-ethylmaleimides probably via a radical mechanism. The 1,3-dioxolanes 2a and 2b were radically polymerized to produce polyacetals by vinyl polymerization. 2c was polymerized to produce randomly containing acetal units and ester units. The mechanism of polymerization of 2e is complex, affording polymers of nonuniform character. 2-Methylene-4-phenyl-1,3-dioxolane polymerization leads to polyester as the main structure, and to a lesser degree polyacetal structures. The chemical structures of the polymers were confirmed by NMR spectra and elemental analysis. © 1996 John Wiley & Sons, Inc.     

The dramatic effect of thiophenol on the reaction pathway of ethyl 4-chloromethyl-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate with thiophenolates: ring expansion versus nucleophilic substitution

Ethyl 4-methyl-2-oxo-7-phenylthio-2,3,6,7-tetrahydro-1H-1,3-diazepine-5-carboxylate and/or ethyl 6-methyl-2-oxo-4-(phenylthiomethyl)-1,2,3,4-tetrahydropyrimidine-5-carboxylate were obtained in the reaction of ethyl 4-chloromethyl-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate with PhSNa or PhSK with or without PhSH, depending on the reagent ratio, reaction time, or temperature, as a result of ring expansion and/or nucleophilic substitution. The reaction pathway was affected strongly by the basicity-nucleophilicity of the reaction media. The results obtained were confirmed by reactions of 4-mesyloxymethyl-6-methyl-5-tosyltetrahydropyrimidin-2-one with PhSNa/PhSH and ethyl 4-chloromethyl-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate with NaCN/HCN or NaCH(COOEt)₂/CH₂(COOEt)₂.     

Comparison of Conventional and Microwave Assisted Reactions Giving Aromatic Oxazolidines

Summary. By reaction of aromatic aldehydes with (-)-ephedrine aromatic 1,3-oxazolidines can be obtained. The reaction was carried out either at conventional conditions or by microwave heating. The different diastereomeric ratios were determined by means of ¹H NMR spectroscopy.Received December 19, 2002; accepted December 23, 2002 Published online June 2, 2003