V. N. Khrustalev

Elaboration of a novel type of planar-chiral methylene bridged biphenols based on [2.2]paracyclophanes

Abstract A new class of chiral methylene bridged biphenols with planar chirality has been designed and elaborated. The synthetic approach is based on the use of 4-hydroxy-5-hydroxymethyl[2.2]paracyclophane 9 derived from either racemic or enantiomerically pure ( S ) - 4 - formyl-5-hydroxy[2.2.]paracyclophane (FHPC) by reduction with LiAlH 4 . The condensation of 9 with chiral racemic 4-hydroxy[2.2]paracyclophane 4 and achiral phenols, such as 2,5-dimethylphenol 10 and 2-isopropyl-5-methylphenol 11 , afforded the target bridged biphenols 6 , 12 and 13 , respectively. The preliminary results on the asymmetric addition of Et 2 Zn to benzaldehyde promoted by ( S,S ) - 6 are reported.

Halo-substituted (S)-N-(2-benzoylphenyl)-1-benzylpyrolidine-2-carboxamides as new chiral auxiliaries for the asymmetric synthesis of (S)-α-amino acids

The synthesis of new chiral auxiliaries (S)-N-(2-benzoylphenyl)-1-(3,4-dichlorobenzyl)-pyrrolidine-2-carboxamide (1a), (S)-N-(2-benzoylphenyl)-1-(pentafluorobenzyl)pyrrolidine-2-carboxamide (1b), and (S)-N-(2-benzoylphenyl)-1-(4-isopropoxytetrafluorobenzyl)pyrrolidine-2-carboxamide (1c) and their application in the asymmetric synthesis of amino acids using NiII complexes of their Schiffs bases with alanine and glycine are described. Compound 1a is particularly appropriate for highly stereoselective synthesis of α-methyl-α-amino acids with high enatiomeric purity (ee >95%).

Oxidative dehydrodimerization of manganese phenylvinylidene complex (η5-C5H5)(CO)2MnCC(H)Ph. X-ray structure of phenyl(trityl)vinylidene complex (η5-C5H5)(CO)2MnCC(CPh3)Ph

Abstract The oxidatively induced dehydrodimerization of the manganese vinylidene complex (η 5 -C 5 H 5 )(CO) 2 MnCC(H)Ph ( I ) to the bis-vinylidene compound (η 5 -C 5 H 5 )(CO) 2 MnCC(Ph)C(Ph)CMn(CO) 2 (η 5 -C 5 H 5 ) ( II ) proceeds via C β H bond homolysis in the radical cation ( I + ) and is thought to involve the formally 16-electron mononuclear σ-phenylethynyl cation [(η 5 -C 5 H 5 )(CO) 2 MnCCPh] + ( III ) and the bis-carbyne dication [(η 5 -C 5 H 5 )(CO) 2 MnCC(Ph)C(Ph)CMn(CO) 2 (η 5 -C 5 H 5 )] 2+ ( II 2+ ) as the key sequential intermediates. Compound II 2+ was characterized by IR and CV. The reduction of II 2+ with (C 6 H 6 ) 2 Cr gave II in an 80% yield. Compound II can be prepared more conveniently by treating I with (C 5 H 5 ) 2 FeBF 4 in the presence of Et 3 N. The interaction of I with Ph 3 CPF 6 yields the trityl(phenyl)vinylidene complex (η 5 -C 5 H 5 )(CO) 2 MnCC(CPh 3 )Ph ( IV ) as a result of the electrophilic attack of the trityl cation on C β followed by the loss of a proton. The structure of IV was established by an X-ray structural analysis.

Nucleophilic vinylic substitution with transition metal carbonyl anions—a rare case of a halophilic reaction mechanism: Formation of halo(acyl)rhenate complexes and X-ray structure of cis-[CF2CF(CO)Re(CO)4Br]Na

Abstract Reactions of polyfluorinated alkenyl halides Z-(CF3)3CCFCFHal (Hal=Cl, I-Cl, Hal=Br, I-Br) and CF2CFBr (II-Br) with [CpFe(CO)2]K (FpK) and [Re(CO)5]Na proceed through the initial attack of metal carbonyl anion on halogen. Reaction with FpK gives minor amounts of σ-alkenyl complexes Z-RfCFCFFe(CO)2Cp (I-Fe, II-Fe) (3–30%), but primarily leads to dimer [CpFe(CO)2]2. Reaction with [Re(CO)5]Na produces anionic halo(acyl)rhenates cis-[Z-RfCFCF(CO)Re(CO)4Hal]Na (V-Cl, V-Br, VI) (70–90%) which were isolated, and halo(acyl)rhenate VI (Rf=F) was characterized by X-ray structure analysis. Halo(acyl)rhenates result from the attack of the intermediate carbanion [RfCFCF]− on the carbonyl ligand of Re(CO)5Hal. The involvement of [RfCFCF]− is demonstrated by their trapping with t-BuOH or CH-acid, which gives the protodehalogenated alkenes I-H and II-H, and suppresses the nucleophilic substitution reaction leading to I-Fe, II-Fe or V-Cl. Arguments against a radical/SET mechanism for the substitution reaction are also advanced.

New subvalent bismuth telluroiodides incorporating Bi2 layers : the crystal and electronic structure of Bi2TeI

Two new subvalent bismuth telluroiodides, Bi2TeI and Bi4TeI1.25, were prepared by the gas-phase synthesis. The compositions of these phases were determined by energy-dispersive X-ray spectroscopy. X-ray diffraction study of melt grown Bi2TeI single crystals demonstrated that the compound crystallizes in the monoclinic system (space group C/2m) with the unit cell parameters a = 7.586(1) Å, b = 4.380(1) Å, c = 17.741(3) Å, β = 98.20°. The layered crystal structure of Bi2TeI consists of weakly bonded two dimensional blocks with a stoichiometry of the title compound. The blocks are stacked along the c axis. Each block consists of eight atomic layers alternating in the Te-Bi-I-Bi-Bi-I-Bi-Te order and includes a double layer of bismuth atoms. Based on the results of ab initio quantum-chemical calculations, the title compound is expected to possess a pronounced anisotropy of conductivity.

Synthesis and molecular structure of 2,3,4,5-tetrahydro-1H-3-benzazepine derivatives and dimethyl 4-cyano-2,3,6,7-tetrahydro-1H-3-benzazonine-5,6-dicarboxylate

A study was carried out on the direction of 1,2,3,4-tetrahydroisoquinolinium quaternary salt rearrangements by the action of base with or without dimethyl acetylenedicarboxylate. These quaternary salts containing a methylene group at the nitrogen atom, are converted in the presence of base through intermediate N-ylides into the Stevens rearrangement products, namely, tetrahydro-3-benzazepines. Upon the addition of dimethyl acetylenedicarboxylate as an electrophilic trap, this diester adds at the carbanion site of the ylide with subsequent recyclization of the piperidine fragment to give a 2-benzazonine derivative with an unusual 4,5-positioning of the olefin bond in the nine-membered heterocycle. An X-ray structural analysis established the molecular structures of 2-cyano-3-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine and dimethyl 4-cyano-2,3,6,7-tetrahydro-1H-3-benzazo-nine-5,6-dicarboxylate.

The nature of the O—O bond in hydroperoxides

Quantum-chemical calculations of the H2O2 and F2 molecules using different computational schemes, basis sets, and procedures for the inclusion of electron correlation were performed. High-resolution X-ray diffraction study of the electron density distribution in the crystals of 2,5-dimethyl-2,5-dihydroperoxyhexane and 2,5-dimethyl-2,5-dihydroperoxyhex-3-yne was carried out. Joint analysis of the results obtained showed that the formally covalent O—O and F—F bonds correspond to a specific type of interatomic interaction. This type is intermediate between the shared and closed-shell interactions (the latter are typical of the ionic systems and van der Waals molecules).

Cage-like Fe,Na-Germsesquioxanes: Structure, Magnetism, and Catalytic Activity

A series of four unprecedented heterometallic metallagermsesquioxanes were synthesized. Their cage-like architectures have a unique type of molecular topology consisting of the hexairon oxo {Fe6 O19 } core surrounded in a triangular manner by three cyclic germoxanolates [PhGe(O)O]5 . This structural organization induces antiferromagnetic interactions between the FeIII ions through the oxygen atoms. Evaluated for this first time in catalysis, these compounds showed a high catalytic activity in the oxidation of alkanes and the oxidative formation of benzamides from alcohols.

New stable germylenes, stannylenes, and related compounds 7. Synthesis and structures of compounds Hal—Sn—OCH2CH2NMe2 (Hal = Cl or F)

New stable divalent tin derivatives containing no bulky substituents at the metal atom, Hal—Sn— OCH2CH2NMe2 (Hal = Cl or F), were synthesized, and their crystal structures were studied by X-ray diffraction. Unlike the analogous monomeric divalent germanium derivative Cl—Ge—OCH2CH2NMe2, the new compounds are centrosymmetric dimers formed via two intermolecular Sn←CO coordination bonds.

Heterocyclization of cycloalkenes with di(2-pyridyl) diselenide in the presence of antimony pentachloride

Cycloalkenes react with di(2-pyridyl) diselenide in the presence of antimony pentachloride with the formation of products of the selenenylating electrophile cycloaddition at the multiple bond. The final products of heterocyclization, chloroantimonates(III) of 2,3-dihydro[1,3]selenazolo[3,2-a]pyridinium derivatives were isolated.