PMR spectra of derivatives of the cis and trans isomers of 4-amino-3-hydroxythiophane

The PMR and proton magnetic double resonance (PMDR) spectra were obtained for five cis and trans isomer pairs of substituted 4-amino-3-hydroxythiophanes. A comparison of the PMR parameters of the cis and trans isomers made it possible to formulate the characteristic differences in their spectra. On the basis of the data obtained, the trans configuration is proposed for the ethoxycarbonylamino and hydroxy groups in 4-ethoxycarbonylamino-3-hydroxy-3-cyanothiophane, the configuration of which has not been previously determined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp.316–319, March, 1971.     

Synthesis of some N-substituted 4,5-dihydro-7,8-dirnethoxybenzothiazepin-3-one 1,1 -dioxides

Reaction of ethyl 3,4-dimethoxyphenylpropionale with chlorosulfonic acid yielded 2-carbo-elhoxyethyl-3,4-dimelhoxybenzene sulfochloride, which was converted to 2-earboethoxyethyl-3,4-dimethoxybenzcnesulfonamides by the action of ammonia or substituted aromatic amines. Alkaline hydrolysis of these sulfonumide esters furnished the corresponding acids. The reaction of acids with phosphorus pentachloride resulted in the key intermediates, the ehloroearboxycthyl-3,4-dimethoxybenzenesulfonamides. The latter was cyelized to N-substituted 4,5-dihydro-7,8-dirnelhoxybenzothizepine-3 -one 1, 1-dioxide. Reactions of benzolhiazepinonc ring and nrnr specttra are described.     

Condensed thiolane 1,1-dioxide systems. 3. Two modes of cyclization of N-substituted trans-3-chloro-4-thioureidothiolane 1,1-dioxides

Reaction of trans-3-chloro-A-aminothiolane 1,1-dioxide hydrochloride with aryl isothiocyanates gives, according to the base involved, cis-perhydrothieno[3,4-d]imidazole-2-thione 5,5-dioxides or the hitherto undescribed cis-2-aryliminoperhydrothieno 3,4-d] thiazole 5,5-dioxides.For Part 2, see [1].Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1420–1423, October, 1988.     

Novel syntheses of cis and trans isomers of combretastatin A-4.

A high-yielding, two-step stereoselective synthesis of the anticancer drug (Z)-combretastatin A-4 (1) has been devised. The method uses the Perkin condensation of 3,4,5-trimethoxyphenylacetic acid and 3-hydroxy-4-methoxybenzaldehyde followed by decarboxylation of the cinnamic acid intermediate using copper and quinoline. The iodine-catalyzed isomerization of the Z isomer 1 results in complete conversion to the E isomer. The Suzuki cross-coupling of an aryl boronic acid and vinyl bromide has also been successfully employed to produce both Z and E isomers of combretastatin A-4 stereoselectively. Both methods are far superior to the current five-step Wittig synthesis in which both isomers are produced nonstereoselectively.     

Synthesis of some N-substituted 6,7-dimethoxy-1,2-benzothiazin(4H)-3-one 1,1-dioxides

Substituted 1,2-benzothiazin-3-ones have been prepared by cyclization of 4,5-dimethoxy-2-carboethoxymethybenzenesulfonamides. The latter were obtained by the action of ammonia and primary and secondary amines on 4,5-dimethoxy-2-carboethoxymethylbenzenesulfonyl chloride which in turn was obtained from ethyl 3,4-dimethoxyphenylacetate and chlorosulfonic acid.     

1,3-Oxazolidin-4-ones. Synthesis and configuration of cis and trans isomers

Mixtures of cis and trans 1,3-oxazolidin-4-ones were obtained by cyclodehydration, in the presence of p-toluenesulfonic acid or boron trifluoride etherate, of lactamide and N-methyl-lactamide with aromatic and aliphatic aldehydes. The products were separated by column (silica) chromatography and their configurations were determined.     

Synthesis and three-dimensional structures of the cis and trans isomers of 3-methyl-1-tert-butyl-4-acetyl- and 3-methyl-1-tert-butyl-4-carbomethoxy-4-piperidols

The cis and trans isomers of 3-methyl-1-tert-butyl-4-acetyl- and 3-methyl-1-tertbutyl-4-carbomethoxy-4-piperidols, the three-dimensional configurations of which were established by means of their IR and UV spectra, were synthesized in order to study the interrelationship between the structure and reactivity of stereoisomeric piperidines.Translated from Khimiya Geterotsiklicheskikh Soedinenni, No.12, pp. 1659–1665, December, 1973.     

Isothiazoles IV: 4-isothiazolin-3-one i-oxide and 1,1-dioxides

Representative 4-isothiazolin-3-one I-oxides and I, I-dioxides have been prepared by the reaction of m-chloroperbenzoic acid with the respective 4-isothiazolin-3-ones. Chromic acid, dinitrogen tetroxide, and nitric acid have also been successfully employed in the oxidation of several 3-hydroxyisothiazoles to their respective I-oxides.     

Vibrational spectra and structures of the cis and trans isomers of linear benzindigo

The resonance Raman and IR spectra of the cis and trans isomers of linear benzindigo were investigated, and the frequencies of the vibrations of the multiple bonds were assigned. The large splitting of the frequencies of the symmetrical (_s) and asymmetrical (_as) vibrations of the carbonyl groups of the trans isomer of benzindigo and indigo is associated with the electronic interaction of these groups in the process of vibration.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 501–504, April, 1981.     

1,3-Dioxolan-4-ones and 1,3-oxathiolan-5-ones. Configuration of cis and trans isomers

The attempted acid-catalyzed azeotropic removal of water from a mixture containing lactamide and chloral in refluxing toluene lead to the elimination of ammonia; both cis- and trans-5-methyi-2-(trichloromethyl)-1,3-dioxolan-4-one were isolated. A number of 1,3-dioxolan-4-ones and 1,3-oxathiolan-5-ones were obtained by cyclodehydration of aldehydes with α-hydroxy- and α-mercapto-carboxylic acids in the presence of boron trifluoride etherate. Geometric isomers were separated, and their configurations were determined by nuclear magnetic resonance.     

Excited-state behavior of trans and cis isomers of stilbene and stiff stilbene: a TD-DFT study

The first part of the isomerization path on the two lowest excited states of trans and cis isomers of stilbene and stiff stilbene is investigated by means of TD-PBE0 calculations in the gas phase and in heptane solution. Solvent effects are taken into account by the PCM model. The excited-state optimized structures and the computed absorption and emission frequencies are in good agreement with the available experimental results. In all of the examined compounds, the isomerization process before barrier crossing occurs on the HOMO --> LUMO bright state, whereas the role played by other single-excitation states appears negligible. The relative energy barriers on the isomerization paths are consistent with the experimental excited-state lifetimes, suggesting a unifying picture of the isomerization process in stilbene-like molecules.     

A convenient synthesis of cis and trans 4-tert-butoxycarbonyl-substituted cyclohexylglycine

A novel synthesis of cis and trans substituted 4-tert-butoxycarbonyl cyclohexylglycines via asymmetric aminohydroxylation of vinyl styrene followed by reduction of the aromatic ring and subsequent oxidation is reported.     

A tungsten-183NMR study of cis and trans isomers of [W(CO)4(PPh3)(PR3)](PR3 = phosphine, phosphite)

Tungsten-183 NMR data are reported for the complexes cis- and trans-[W(CO)4(PPh3)(PR3)] (PR3 = PnBu3, PMe3, PMe2Ph, PMePh2, PPh3, P(4-C6H4OMe)3, P(4-C6H4Me)3, P(4-C6H4F)3, P(OMe)3, P(OEt)3, P(OPh)3 and for PCy3, P(NMe2)3(trans isomer only). The 183W chemical shift (obtained by indirect detection using 31P) is found to be related to the PR3 ligand parameters nu and theta (Tolman electronic factor and cone angle, respectively) for the cis isomers and to nu (but only poorly to theta) for the trans isomers. The 183W-31P spin coupling constant is also related, less clearly for P-C than for P-N and P-O bonded ligands, to nu. Chemical shifts are referenced to an absolute frequency Xi (183W) = 4.15 MHz, which is proposed as a calibration standard for 183W NMR. The structures of cis-[W(CO)4(PPh3)(PMe3)] and cis-[W(CO)4(PPh3){P(4-C6H4F)3}] are reported.     

A synthesis of 4-carboxy-3-methylceph-3-em 1,1-dioxide involving a new strategy for the ring enlargement of penicillanate 1,1-dioxides

The title compound has been prepared from sulbactam sodium salt by a six-step sequence.