4- And 5-hydroxylaminothiazolidine-2-thiones. Rearrangement of the carbamoyl derivatives to 4- and 5-ureidothiazolidin-2-ones

The carbamoylation of 4- and 5-hydroxyaminothiazolidine-2-thiones by methyl and 3,4-dichlorophenyl isocyanates leads to the corresponding hydroxyureas, which rearrange to 4- and 5-ureidothiazolidin-2-ones on heating in the presence of a base. Under these conditions, the hydroxyurea based on 5-hydroxylaminothiazolidin-2-one is converted to 5-ureidooxazolidin-2-one.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1678–1682, December, 1987.     

Pyrroles from ketoximes and acetylene. 43. 1,2-Dihaloalkanes and vinyl chloride in the synthesis of 2-(4-alkylthiophenyl)pyrroles

2-(4-Alkylthiophenyl)-3- and 2-(4-alkylthiophenyl)-5-methylpyrroles and their 1-vinyl derivatives were synthesized by the reaction of alkyl(4-alkylthiophenyl)ketoximes with dihaloalkanes or vinyl chloride in the KOH-DMSO system at 120–140C and atmospheric pressure.See [1] for Communication 42.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1, 1337–1340, October, 1990.     

Pyridine-substituted hydroxythiophenes. II. Alkylation of o-(2-, 3- and 4-pyridyl)-3-hydroxythiophenes: Regiospecific formation of o-pyridyl-3-alkoxythiophenes

The alkylation of o-(2-, 3- and 4-pyridyl)-3-hydroxythiophenes has been investigated. In the case of 4-(2-, 3- and 4-pyridyl)-3-hydroxythiophene systems, the soft alkylating reagent, methyl iodide, using sodium hydride as the base and dimethylimidazolidinone as the solvent, gave rise to a mixture of O-alkylated and O,C-dialkylated products in the proportions of 4.6–6.5 to 1. However, in the case of 2-(2-, 3- and 4-pyridyl)-3-hydroxythiophene systems, the same reaction conditions brought about exclusively O-alkylated compounds in yields of 45–53%. In both cases, the hard alkylating reagent, methyl p-toluenesulfonate, with the same base and solvent, only give O-alkylated compounds in yields of 51–77%. These latter conditions resulted in a good preparative route for the regiospecific formation of o-pyridyl-3-alkoxythiophenes by using ethyl 2-bromopro-pionate as well as methyl p-toluenesulfonate as alkylating reagents. The hydrolysis of the esters, derived from alkylation with ethyl 2-bromopropionate, has also been investigated.     

A pathway to 3-(β-D-ribofuranosyl)-4-nitro-5-ethoxycarbonyl-isoxazoles,useful in the synthesis of pyrazofurin analogues

The synthesis of 3-cyclohexyl and 3-β-D-ribofuranosyl-4-nitro-5-ethoxycarbonyl isoxazole, is realized by conversion of cyclohexane carboxaldehyde and 2,5-anhydro-3,4,6-tri-O-benzoyl-D-allose into the corresponding nitromethyloximes followed by reaction with ethylchlorooxoacetate.     

Studies on the synthesis of (2S,3R)-3-hydroxy-3-methylproline via C2-N bond formation

A new efficient synthesis of (2S,3R)-3-hydroxy-3-methylproline (3) is reported. During the course of a recent study on the Lewis acid promoted intramolecular opening of an epoxide by a carbamate NH, a highly concerted rearrangement was unexpectedly observed. Further investigations of substrate generality show that delta-carbamate-alpha,beta-epoxide esters commonly underwent similar rearrangements with the aid of Lewis acids. Retrosynthetic analysis of such a C(2)-N disconnection can lead to an efficient synthesis of (2S,3R)-3-hydroxy-3-methylproline (3) in high enantio purity. Stereochemistries were established by a Sharpless asymmetric dihydroxylation and a diastereoselective reductive amination.     

Alpha,2-, alpha,3-, and alpha,4-dehydrophenol radical anions: formation,reactivity, and energetics leading to the heats of formation of alpha,2-, alpha,3-, and alpha,4-oxocyclohexadienylidene

We have regiospecifically generated the alpha,2-, alpha,3-, and alpha,4-dehydrophenoxide anions by collisional activation of o-, m-, and p-nitrobenzoate. The alpha,2 and alpha,4 isomers also were synthesized by reacting o-benzyne radical anion with carbon dioxide and electron ionization of p-diazophenol. All three dehydrophenol radical anions were differentiated from each other and identified by probing their chemical reactivity with several reagents. Each isomer was converted to phenoxide and its corresponding quinone as well. Thermochemical measurements were carried out on all three radical anions and their hydrogen-atom affinities, proton affinities, and electron binding energies are reported. These measured quantities are combined in thermodynamic cycles to derive the heats of formation of each of the radical anions and their corresponding carbenes (i.e., alpha,2-, alpha,3-, and alpha,4-dehydrophenol). These results are compared to MCQDPT2, G3, G2+(MP2), and B3LYP calculations and experimental data for appropriate reference compounds.     

Diastereoselective synthesis of 4-substituted 5-(p-tolylsulfinyl)-5,6-dehydropiperidin-2-ones. A new approach to methyl l-(2S,4S)-4-methyl-6-oxopipecolate

The sulfoxide-mediated diastereoselective Michael reaction of homochiral α-sulfinylketimines 1a–d and β-substituted ene esters 2a–d (Hua's reaction) was explored. Straightforward cyclization of the open-chain adducts take place under the reaction conditions to provide the 4-substituted 5-(p-tolylsulfinyl)-5,6-dehydropiperidin-2-ones 3 and 7–12, whose stereochemistry is formed in the prior step. Furthermore, the role of the metal ion of the aza-enolate reagents and the steric demands of the O-alkyl ester group have been examined. It seems that the anti-diastereoselectivity depends on metal chelation by the oxygen of the ester as well as the oxygen of the sulfinyl group and the nitrogen in the aza-enolate ((Z)-configuration). In addition, the synthesis of methyl l-(2S,4S)-4-methyl-6-oxopipecolate has been achieved from the suitably functionalized 2-sulfinylketimine 1a (five steps; overall yield: 53–65%).     

Clathrate formation in the [M(4-MePy)2 (NCS)2]-4-MePy systems,where M=Co(II), Ni(II), Zn(II), Cd(II); 4-MePy=4-methylpyridine

A number of complexes [M(4-MePy)_n (NCS)₂], where M=Co(II), Ni(II), Zn(II), Cd(II); n=2 or 4 have been synthesized and phase diagrams [M(4-MePy)₂(NCS)₂]-4-MePy have been studied. The forming compounds have been obtained and described with the help of IR-spectroscopy and thermal analysis. The structure of a molecular type with variable section channels, filled by two types guest-molecules (by a water molecule in the narrow part of the channel and by two 4-methylpyridine molecules in the broad part of the channel, with a total ratio guest: host being 1:1) for [Cd(4-MePy)₄ (NCS)₂]·0.67(4-MePy)·0.33H₂O has been defined by X-ray method. This clathrate is isostructural (X-ray powder diffractogram) to the anhydrous compound [Cd(4-MePy)₄ (NCS)₂]·0.67(4-MePy).     

配位化学中的直线自由能关系XXI: 铜(II)-13-取代苄基-1, 4, 8, 11-四氮杂环十四烷-12, 14-二酮配合物的生成及酸分解行为研究

采用pH法, 在25.0±0.1℃, I=0.1 mol.dm^-^3 (KNO3)条件下, 测定了13-取代苄基-1, 4, 8, 11-四氮杂环十四烷-12,14-二酮的质子化常数及其与Cu(II)配位的平衡常数。讨论了配体与金属离子的配位方式。在25.0±0.1℃, 离子强度为0.1mol.dm^-^3 (KNO3)下, 采用分光光度法, 研究了这些配体铜(II)配合物的酸分解动力学行为。探讨了配合物酸分解机理,得到了速控步的速率常数。发现配位反应平衡常数与配体的质子化常数及配合物酸分解反应速率常数之间存在较好的Hammett型和Bronsted型直线自由能关系。同时探讨了取代基对配合物生成及酸分解的影响情况。     

Stereospecific synthesis of (+) -cahbocyclic 2'-deoxyadenosine. an improved procedure for the preparation of (+)-(1r,2s,4r)-4-amino-2-hydroxy-1-hydroxymethylcyclopentane.

An improved procedure for the preparation of a versatile synthetic precursor, (+)-13, of carba-2'-deoxyribonucleosides and the first stereospecific way to enantiomerically pure carbocyclic 2'-deoxyadenosine, (+)-14, are presented from bicyclic lactone diol (+)-1. An unexpected formation of the disubstituted 2-oxabicyclo[2.2.1]heptane skeleton 15 through a hypervalent iodo species derived from 6 is also reported.     

(4R,6R)-6-(hydroxymethyl)-4-methyltetrahydro-2H-pyran-2-one in the synthesis of polyfunctional compounds with the methyl-branched carbon skeleton

A simple and efficient asymmetrical synthesis was performed of a convenient bifunctional building block, methyl (R)-5,5-dimethoxy-3-methylpentanoate and its (S)-enantiomer. The possibility was shown of its application to the synthesis of insect pheromones.     

Studies on the synthesis of indole alkaloids of condylocarpine type. C-4 alkylation of the 1-alkyl-3-(hydrazono)-2-piperidone system

A method for C-4 alkylation of the 1-alkyl-3-(hydrazono)-2-piperidone system (α-ketoamide hydrazone) is described. Attempts to apply it to an intramolecular alkylation for the creation of a condylocarpine alkaloid intermediate failed.     

Beta-lactam antifungals. II. Enantiocontrolled synthesis of (2R,5S)-2-hydroxymethyl-1-carbapenam, the carba-analog of a clavam antifungal.

(2R,5S)-2-Hydroxymethyl-1-carbapenam (3), the carba-analog of an antifungal beta-lactam (2R,5S)-2-(hydroxymethyl)calvam (1), was synthesized in an enantiocontrolled manner, starting from the coupling reaction of an optically active phthalimido-acetate (3S,4S)-4 and an allylsilane 7, followed by removal of the phthalimido group that was crucial for asymmetric induction. Hydroboration, protecting-group interconversion, and cyclization gave 3 stereoselectively.