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A convenient one-step synthesis of chiral γ-lactones has been performed. The method is based on enantioselective hydrogenation of γ-ketoesters using the RuCl 3 –BINAP–HCl catalytic system. Chiral γ-lactones (91–99% ee) have been isolated in 57–88% yield.

The rate of hydrogenation of γ-ketoesters MeCOCH2CH2COOR (R = Et, Pri, But) in the presence of the chiral RuII—BINAP catalyst (BINAP is 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) greatly increases upon the addition of 5–10 equivalents of HCl with respect to ruthenium. In the hydrogenation of ethyl levulinate, the optically active γ-hydroxy ester initially formed would cyclize by ∼95% to give γ-valerolactone with optical purity of 98–99% ee. When the Ru(COD)(MA)2—BINAP—HCl catalytic system is used (COD is 1,5-cyclooctadiene, MA is 2-methylallyl), complete conversion of the ketoester (R = Et) in EtOH is attained in 5 h at 60 °C under an H2 pressure of 60–70 atm.

An improved procedure was developed for asymmetric reduction of acetophenone and propiophenone by the chiral reagent NaAl(IPTOLate)H2. This procedure is based on isolation of the chiral alcohol that formed as a crystalline host—guest complex with the IPTOL ligand. The enantiomeric enrichment of the product was as high as 97% ee. The ability of IPTOL and its analogs to form host—guest complexes with a number of ether-type solvents, 1-phenylethanol, and 1-phenylpropan-1-ol as well as thermal stabilities of IPTOL-containing complexes with these alcohols were studied.

Prochiral substrates (alkyl aryl ketones, cyclopropyl methyl ketone, 1-indanone, 1-tetralone, ethyl 2-oxo-4-phenylbutyrate, and N-(diphenylphosphinyl)acetophenoneimine) were subjected to asymmetric reduction with aluminum hydride reagents, which were prepared by modifications of NaAlH4 or AlH3 with chiral α,α,α",α"-tetraaryl-1,3-dioxolane-4,5-dimethanols (TADDOL). The effects of the nature of the substituents in TADDOL, the structure of the prochiral substrate, and the reaction conditions on the stereochemistry of reduction were investigated. The highest enantioselectivity (70—90% ee) was achieved upon reduction of alkyl aryl ketones and N-(diphenylphosphinyl)acetophenoneimine with NaAl(TADDOLate)H2 in THF or diglyme at a temperature from –70 to –20 °C. The mechanism of asymmetric induction in the reduction reactions of ketones with aluminum hydride reagents is discussed. The stereochemical results of reduction were explained by comparing three-dimensional models of the most probable transition states.

New stereoselective reducing reagents were preparedin situ by modification of NaAlH4 with various chiral diols. The efficiency of 1,4- and 1,3-diols as chiral auxiliaries in the reactions of alkyl aryl ketones with modified NaAlH4 was considerably higher than that of 1,2-diols. The effect of the nature of the achiral ligand additionally introduced into the chiral hydride reagent on the enantioselectivity of ketone reduction was studied. It was proposed that the sodium cation does not necessarily participate at the stage governing the reaction stereochemistry.

A comparative study of asymmetric hydrogenation and deuteration of methyl levulinate catalyzed by the RuII—(S)-BINAP—HCl system (BINAP is 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) in MeOH and MeOD was carried out. The results obtained suggest an important role of the protic solvent in the formation of catalytically active ruthenium complexes.

A convenient preparative synthesis of cilastatin, an inhibitor of renal dipeptidase used in drugs with the antibiotic imipenem, has been elaborated. The key intermediate in this synthesis is 2-amino-7-chloroheptanoic acid prepared by oxidative cleavage of cycloheptanone followed by bromination of 7-chloroheptanoyl chloride with subsequent amination of the 2-bromo-7-chloroheptanoic acid thus formed. All of the stages of the new synthesis are easily performed, as is the isolation of the intermediate products, and they do not require any organometallic reagents.

A study has been made of the asymmetric hydrosilylation of acetophenone by diphenylsilane under the influence of rhodium complexes with chiral phosphites. The enantioselective nature of the reaction depends on the phosphite structure, the acetophenone/rhodium and ligana/rhodium ratios, and the temperature. The maximum optical yield (24%) is attainod on the complex [Rh(COD)Cl]2/(S, S)-2-ethoxy-4,5-dicarbisopropoxy-1,3-2-dioxophiospholane.

Asymmetric hydrosilylation of acetophenoxime and cyclic and acyclic imines (with subsequent hydrolysis to amines) was investigated using as catalyst a rhodium complex with the chiral phosphinamino ligand (S)-Phephos. With this method the chiral analog of the antidepressant Pyrazidol was synthesized with an optical yield of 73%.

Enantioselective hydrogenation of ethyl 4-chloro-3-oxobutyrate in ionic liquid systems containing tetraethylammonium bromide, 1-butyl-3-methylimidazolium hexafluorophosphate, or 1-butyl-3-methylimidazolium trifluoromethanesulfonate in the presence of the chiral catalyst Ru-BINAP ensures a high level of asymmetric induction after at least threefold recycling of the catalyst.

A selective method for the preparation of 5-chloropentan-2-one by interaction of 1-methylcyclobutanol with Ca(OCl)2 followed by decomposition of the hypochlorite thus obtained in the presence of FeII salt is proposed. The selectivity of the ketone formation from the alcohol is 98%, while the conversion of the alcohol is 35–40%.

New stereoselective reducing reagents were preparedin situ by modification of NaAlH4 with various chiral diols. The efficiency of 1,4- and 1,3-diols as chiral auxiliaries in the reactions of alkyl aryl ketones with modified NaAlH4 was considerably higher than that of 1,2-diols. The effect of the nature of the achiral ligand additionally introduced into the chiral hydride reagent on the enantioselectivity of ketone reduction was studied. It was proposed that the sodium cation does not necessarily participate at the stage governing the reaction stereochemistry.

The binuclear structure of complex (IIa) is indicated by the finding of a mass spectral peak with m/z 971 and IR absorption band for the bridging bond VRh_Cl = 294 cm -I. X-ray photoelectron spectroscopy showed bidentate coordination for ligand (IIa). The increase in the energy of the bond energies of the 2p electrons of phosphorus and is electrons of nitrogen upon going from the free ligand (131.0 and 398.6 eV) to the coordinated ligand (132.6 and 400.6 eV) indicates the formation of Rh-P and Rh-N bonds in the solid samples of complex (IIa). The lack of resolution in the iH and 31p NMR spectra of solutions of (IIa) at 20~ and the appearance of a doublet in the 31p NMR spectrum of this complex in CH2CI 2 at -80~ (6P = 33.9 ppm, iJP,Rh = 151.1 Hz) is evidence for rapid dissociation and formation of the Rh-N bond. Analysis of the IH NMR spectrum of complex (IIb) (splittihg of the doublet for the protons of the methyl group bound to the CH group and broadening of the signai for the protons of the methyl groups at the nitrogen atom) and its ~ip NMR spectrum (doublet, 5P = 20.5 ppm, IJP,Rh = 168.0 Hz) suggests coordination of the phosphorus and nitrogen atoms by rhodium'and the existence of two conformers of this complex (IIb) [2].

1. N-Acetylaminocinnamic acid is hydrogenated enantioselectively in the presence of [Rh(R-PheNOP)(COD)]C1O4 with the formation of up to 60% optical yields of S-N-acetylphenylalanine. 2. The optical yield is increased with increase in the hydrogen pressure to 20 atm and with decrease in temperature and depends on the dielectric constant of the solvent. 3. The optical yield is greatly reduced when the reaction is carried out in the presence of triethylamine.

1. Primary alcohols are dehydrogenated on samarium oxide to a greater degree than they are dehydrated, and the dehydrogenating ability increases as the molecular weight of the primary alcohols is increased. Secondary isopropanol is dehydrated to a greater degree. 2. On samarium oxide, alkyl substituants on the α- and β-carbon atoms, when two hydrogen atoms are replaced by methyl, exert a great influence on the value of the activation energy of dehydrogenation. 3. The bond energies of C, H, and O with Sm2O3 were determined by a kinetic method.

1. During the catalytic synthesis of piperazine from monoethanolamine in the presence of Co/Al2O3, complex compounds are formed. 2. The product isolated as a result of treatment of the catalyst after the reaction represents a complex of Co3+ with various amines contained in the reaction mixture. 3. A scheme was proposed for the formation of piperazine from monoethanolamine on the catalyst Co/Al2O3; the individual steps of the catalytic process were described in the terms of coordination chemistry.